2002 AMC 8 Problems

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All problems are used with official legal permission of the Mathematical Association of America (MAA).

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1.

A circle and two distinct lines are drawn on a sheet of paper. What is the largest possible number of points of intersection of these figures?

22

33

44

55

66

Answer: D
Concepts:counting intersectionsoptimization
Difficulty rating: 370
Small Hint:

Count each type of pair of figures separately.

Big Hint:

Each line can meet the circle at most twice, and the two lines can meet once.

Solution:

A line and a circle can intersect at no more than two points, and two distinct lines can intersect at no more than one point.

Arrange the two lines so each meets the circle twice and the two lines meet at a different point. This gives 2+2+1=5.2+2+1=5.

Thus, D is the correct answer.

2.

How many different combinations of $5\$5 bills and $2\$2 bills can be used to make a total of $17?\$17? Order does not matter in this problem.

22

33

44

55

66

Answer: A
Difficulty rating: 610
Small Hint:

Because $17\$17 is odd, the number of $5\$5 bills must be odd.

Big Hint:

Try the possible odd numbers of $5\$5 bills before the total goes over $17.\$17.

Solution:

Since the total $17\$17 is odd, the number of $5\$5 bills must be odd.

One $5\$5 bill leaves $12,\$12, which is six $2\$2 bills. Three $5\$5 bills leave $2,\$2, which is one $2\$2 bill. Five $5\$5 bills is too much.

Therefore, there are 22 combinations.

Thus, A is the correct answer.

3.

What is the smallest possible average of four distinct positive even integers?

33

44

55

66

77

Answer: C
Difficulty rating: 560
Small Hint:

To make the average as small as possible, choose the smallest possible integers.

Big Hint:

Use the four smallest distinct positive even integers.

Solution:

To get the smallest possible average, we want to use the smallest 44 positive even integers.

This can be achieved as follows: 2+4+6+84=204 \dfrac{2 + 4 + 6 + 8}{4} = \dfrac{20}{4}=5. = 5.

Thus, C is the correct answer.

4.

The year 20022002 is a palindrome (a number that reads the same from left to right as it does from right to left). What is the product of the digits of the next year after 20022002 that is a palindrome?

00

44

99

1616

2525

Answer: B
Difficulty rating: 660
Small Hint:

The next palindrome after 20022002 still starts and ends with 2.2.

Big Hint:

The middle two digits must increase to the smallest matching pair.

Solution:

We don’t want to increase the thousands digit, so we can keep that as 2.2.

This means that we have to increase the tens and hundreds digits to 1,1, to yield the next palindrome of 2112.2112. The product of its digits is 4.4.

Thus, B is the correct answer.

5.

Carlos Montado was born on Saturday, November 9,9, 2002.2002. On what day of the week will Carlos be 706706 days old?

Monday

Wednesday

Friday

Saturday

Sunday

Answer: C
Difficulty rating: 730
Small Hint:

Reduce 706706 modulo 7.7.

Big Hint:

700700 days is an exact number of weeks.

Solution:

The days of the week cycle every 77 days. After 700700 days, the day of the week will still be Saturday.

After 66 more days, the day of the week will be Friday.

Thus, C is the correct answer.

6.

A birdbath is designed to overflow so that it will be self-cleaning. Water flows in at the rate of 2020 milliliters per minute and drains at the rate of 1818 milliliters per minute. One of these graphs shows the volume of water in the birdbath during the filling time and continuing into the overflow time. Which one is it?

Answer: A
Difficulty rating: 820
Small Hint:

Before overflow, the volume rises at a constant positive rate.

Big Hint:

After the birdbath is full, extra water overflows so the volume stays constant.

Solution:

Before the birdbath overflows, it gains 2018=220-18=2 milliliters of water per minute, so its volume increases steadily.

Once the birdbath is full, the incoming extra water overflows, so the volume remains constant. Only graph A shows an increasing line followed by a horizontal line.

Thus, A is the correct answer.

7.

The students in Mrs. Sawyer’s class were asked to do a taste test of five kinds of candy. Each student chose one kind of candy. A bar graph of their preferences is shown. What percent of her class chose candy E?E?

55

1212

1515

1616

2020

Answer: E
Difficulty rating: 860
Small Hint:

Add the heights of all five bars to get the class size.

Big Hint:

Compare the height of bar EE with the total number of students.

Solution:

There are a total of 6+8+4+2+5=25 6 + 8 + 4 + 2 + 5 = 25 students in the class. The percent that chose EE is 100525=1005=20%. 100 \cdot \dfrac{5}{25} = \dfrac{100}{5} = 20 \%.

Thus, E is the correct answer.

8.

Problems 8,8, 9,9, and 1010 use the data found in the accompanying paragraph and table.

Juan’s Old Stamping Grounds

Juan organizes the stamps in his collection by country and by the decade in which they were issued. The prices he paid for them at a stamp shop were: Brazil and France, 66¢ each, Peru 44¢ each, and Spain 55¢ each. (Brazil and Peru are South American countries and France and Spain are in Europe.)

Number of Stamps by Decade

How many of his European stamps were issued in the ‘8080s?

99

1515

1818

2424

4242

Answer: D
Difficulty rating: 890
Small Hint:

European means France and Spain in the table.

Big Hint:

Use only the entries in the ‘8080s column.

Solution:

Note that France and Spain are the European countries. The number of ‘8080s stamps from these countries respectively is 1515 and 99 for a total of 15+9=24 15 + 9 = 24 stamps.

Thus, D is the correct answer.

9.

His South American stamps issued before the ‘7070s cost him

$0.40\$0.40

$1.06\$1.06

$1.80\$1.80

$2.38\$2.38

$2.64\$2.64

Answer: B
Difficulty rating: 1010
Small Hint:

South American means Brazil and Peru.

Big Hint:

Before the ‘7070s means the ‘5050s and ‘6060s columns.

Solution:

Brazil and Peru are the South American countries.

Brazil has 4+7=114+7=11 stamps before the ‘7070s, costing 116=6611\cdot6=66 cents. Peru has 6+4=106+4=10 such stamps, costing 104=4010\cdot4=40 cents.

The total cost is 66+40=10666+40=106 cents, or $1.06.\$1.06.

Thus, B is the correct answer.

10.

The average price of his ‘7070s stamps is closest to

3.53.5¢

44¢

4.54.5¢

55¢

5.55.5¢

Answer: E
Difficulty rating: 1070
Small Hint:

Compute the total cost of all ‘7070s stamps.

Big Hint:

Divide the total cost by the number of ‘7070s stamps, then choose the closest option.

Solution:

The ‘7070s stamps cost 126+126+64+135=72+72+24+65=233 \begin{aligned} &12\cdot6+12\cdot6 \\ &\quad {}+6\cdot4+13\cdot5 \\ &\quad {}=72+72+24+65 \\ &\quad {}=233 \end{aligned} cents.

There are 12+12+6+13=4312+12+6+13=43 stamps, so the average cost is 233÷43,233\div43, a little more than 55 cents and closest to 5.55.5 cents.

Thus, E is the correct answer.

11.

A sequence of squares is made of identical square tiles. The edge of each square is one tile length longer than the edge of the previous square. The first three squares are shown. How many more tiles does the seventh square require than the sixth?

1111

1212

1313

1414

1515

Answer: C
Difficulty rating: 1060
Small Hint:

The sixth and seventh squares have side lengths 66 and 7.7.

Big Hint:

Compare 727^2 and 62.6^2.

Solution:

The sixth and seventh squares have side lengths 66 and 77 tile lengths.

They use 62=366^2=36 and 72=497^2=49 tiles, respectively, so the seventh square requires 4936=1349-36=13 more tiles.

Thus, C is the correct answer.

12.

A board game spinner is divided into three regions labeled A,A, BB and C.C. The probability of the arrow stopping on region AA is 13\frac{1}{3} and on region BB is 12.\frac{1}{2}. The probability of the arrow stopping on region CC is

112\dfrac{1}{12}

16\dfrac{1}{6}

15\dfrac{1}{5}

13\dfrac{1}{3}

25\dfrac{2}{5}

Answer: B
Difficulty rating: 1090
Small Hint:

The probabilities of A,A, B,B, and CC add to 1.1.

Big Hint:

Subtract the probabilities for AA and BB from 1.1.

Solution:

The total probability is 1.1. We need to subtract the probability of the spinner landing on BB and AA to get C,C, which is 11312=16. 1 - \dfrac{1}{3} - \dfrac{1}{2} = \dfrac{1}{6}.

Thus, B is the correct answer.

13.

For his birthday, Bert gets a box that holds 125125 jellybeans when filled to capacity. A few weeks later, Carrie gets a larger box full of jellybeans. Her box is twice as high, twice as wide and twice as long as Bert’s. Approximately, how many jellybeans did Carrie get?

250250

500500

625625

750750

10001000

Answer: E
Difficulty rating: 1140
Small Hint:

Doubling length, width, and height multiplies volume by 222.2\cdot2\cdot2.

Big Hint:

Scale the number of jellybeans by the volume factor.

Solution:

The larger box will have approximately 125222=1000 125 \cdot 2 \cdot 2 \cdot 2 = 1000 jellybeans.

Thus, E is the correct answer.

14.

A merchant offers a large group of items at 30%30\% off. Later, the merchant takes 20%20\% off these sale prices and claims that the final price of these items is 50%50\% off the original price. The total discount is

35%35\%

44%44\%

50%50\%

56%56\%

60%60\%

Answer: B
Concepts:percentage
Difficulty rating: 1180
Small Hint:

After a 30%30\% discount, 70%70\% of the original price remains.

Big Hint:

The second discount is 20%20\% off the sale price, not the original price.

Solution:

Let the original price be x.x. After the 30%30\% discount, the price is 0.70x.0.70x.

Taking another 20%20\% off that sale price leaves 0.800.70x=0.56x.0.80\cdot0.70x=0.56x.

The customer pays 56%56\% of the original price, so the total discount is 44%.44\%.

Thus, B is the correct answer.

15.

Which of the following polygons has the largest area?

A\text{A}

B\text{B}

C\text{C}

D\text{D}

E\text{E}

Answer: E
Difficulty rating: 1290
Small Hint:

Break each polygon into unit squares and half-unit triangles.

Big Hint:

Compare the five areas by counting full squares plus half-squares.

Solution:

The number of boxes enclosed by each polygon can be obtained by dividing the polygon into unit squares and right triangles with sidelength 11 and adding up their values.

The unit squares count as 11 and the triangles count as 0.5.0.5.

AA has a total area of 5,5, BB has 5,5, CC has 5,5, DD has 4.5,4.5, and EE has 5.5.5.5.

Thus, E is the correct answer.

16.

Right isosceles triangles are constructed on the sides of a 3453-4-5 right triangle, as shown. A capital letter represents the area of each triangle. Which one of the following is true?

X+Z=W+YX + Z = W + Y

W+X=ZW + X = Z

3X+4Y=5Z3X + 4Y = 5Z

X+W=12(Y+Z)X + W = \dfrac{1}{2}(Y + Z)

X+Y=ZX + Y = Z

Answer: E
Difficulty rating: 1310
Small Hint:

Each right isosceles triangle has area half the square of the side it is built on.

Big Hint:

Compute the areas on the sides 3,3, 4,4, and 5.5.

Solution:

For a right isosceles triangle built on a side of length s,s, the two legs have length s,s, so its area is s22.\frac{s^2}{2}.

W=342=6,X=322=4.5,Y=422=8,Z=522=12.5. \begin{aligned} &W=\frac{3\cdot4}{2}=6, \\ &\quad X=\frac{3^2}{2}=4.5, \\ &\quad Y=\frac{4^2}{2}=8, \\ &\quad Z=\frac{5^2}{2}=12.5. \end{aligned}

These values satisfy X+Y=Z,X+Y=Z, and the other listed equations do not.

Thus, E is the correct answer.

17.

In a mathematics contest with ten problems, a student gains 55 points for a correct answer and loses 22 points for an incorrect answer. If Olivia answered every problem and her score was 29,29, how many correct answers did she have?

55

66

77

88

99

Answer: C
Difficulty rating: 1290
Small Hint:

Let xx be the number of correct answers.

Big Hint:

Then the number of incorrect answers is 10x.10-x.

Solution:

Let xx be the number of correct answers. Then she answered 10x10 - x questions incorrectly.

This gives her a total score of 5x2(10x)=7x20. 5x - 2(10 - x) = 7x - 20.

We know that this equals 29,29, and solving yields 7x20=29 7x - 20 = 29 x=7. x = 7.

Thus, C is the correct answer.

18.

Gage skated 11 hr 1515 min each day for 55 days and 11 hr 3030 min each day for 33 days. How long would he have to skate the ninth day in order to average 8585 minutes of skating each day for the entire time?

11 hr

11 hr 1010 min

11 hr 2020 min

11 hr 4040 min

22 hr

Answer: E
Difficulty rating: 1360
Small Hint:

Convert all skating times to minutes.

Big Hint:

Find the total minutes needed for a 99-day average of 85.85.

Solution:

Gage has skated a total of 575+390=645 5 \cdot 75 + 3 \cdot 90 = 645 minutes.

For an average of 8585 minutes over 99 days, Gage must have skated a total of 859=765 85 \cdot 9 = 765 minutes.

This means that Gage must skate 765645=120 765 - 645 = 120 minutes on the last day. Note that 120120 minutes is the same as 22 hours.

Thus, E is the correct answer.

19.

How many whole numbers between 9999 and 999999 contain exactly one 0?0?

7272

9090

144144

162162

180180

Answer: D
Difficulty rating: 1390
Small Hint:

The number is a three-digit number.

Big Hint:

The single 00 can be in the tens place or the ones place, but not the hundreds place.

Solution:

Note that the 00 digit can either be the tens or the units digit. This gives us 22 options for this.

There are 99 options for each of the other digits for a total of 299=162 2 \cdot 9 \cdot 9 = 162 numbers.

Thus, D is the correct answer.

20.

The area of triangle XYZXYZ is 88 square inches. Points AA and BB are midpoints of congruent segments XY\overline{XY} and XZ.\overline{XZ}. Altitude XC\overline{XC} bisects YZ.\overline{YZ}. The area (in square inches) of the shaded region is

1121 \frac{1}{2}

22

2122 \frac{1}{2}

33

3123 \frac{1}{2}

Answer: D
Difficulty rating: 1450
Small Hint:

The altitude splits the isosceles triangle into two equal halves.

Big Hint:

The segment through the midpoints creates a similar triangle with half the side lengths.

Solution:

Since XY=XZXY=XZ and XCXC bisects YZ,YZ, altitude XCXC splits XYZ\triangle XYZ into two congruent triangles. The left half XYC\triangle XYC has area 4.4.

In XYC,\triangle XYC, point AA is the midpoint of XY.XY. The horizontal segment through AA meets XCXC halfway up, so the small top triangle is similar to XYC\triangle XYC with scale factor 12.\frac{1}{2}. Its area is therefore 14\frac{1}{4} of 4,4, or 1.1.

The shaded region is the rest of the left half, so its area is 41=3.4-1=3.

Thus, D is the correct answer.

21.

Harold tosses a nickel four times. The probability that he gets at least as many heads as tails is

516\dfrac{5}{16}

38\dfrac{3}{8}

12\dfrac{1}{2}

58\dfrac{5}{8}

1116\dfrac{11}{16}

Answer: E
Difficulty rating: 1550
Small Hint:

At least as many heads as tails means 2,2, 3,3, or 44 heads.

Big Hint:

Count outcomes by choosing which tosses are heads.

Solution:

There are 24=162^4=16 equally likely outcomes for four coin tosses.

At least as many heads as tails means getting 2,2, 3,3, or 44 heads. The number of such outcomes is (42)+(43)+(44)=6+4+1=11. \begin{aligned} &\binom{4}{2}+\binom{4}{3}+\binom{4}{4} \\ &\quad {}=6+4+1=11. \end{aligned}

Thus the probability is 1116.\dfrac{11}{16}.

Thus, E is the correct answer.

22.

Six cubes, each an inch on an edge, are fastened together, as shown. Find the total surface area in square inches. Include the top, bottom, and sides.

1818

2424

2626

3030

3636

Answer: C
Difficulty rating: 1550
Small Hint:

Start with 66 separate cubes, each with 66 exposed faces.

Big Hint:

Each glued pair of faces removes two exposed faces.

Solution:

We can count the number of unexposed faces to find how many faces contribute to the surface area.

Three cubes have 11 face unexposed, two cubes have 22 faces unexposed, and one cube has 33 faces unexposed.

This gives us a total of 31+22+13=10 3 \cdot 1 + 2 \cdot 2 + 1 \cdot 3 = 10 unexposed faces, which gives us 6610=3610 6 \cdot 6 - 10 = 36 - 10 =26= 26 exposed faces.

Each exposed face contributes 12=11^2 = 1 to the surface area, for a total surface area of 126=26.1 \cdot 26 = 26.

Thus, C is the correct answer.

23.

A corner of a tiled floor is shown. If the entire floor is tiled in this way and each of the four corners looks like this one, then what fraction of the tiled floor is made of darker tiles?

13\dfrac{1}3

49\dfrac{4}9

12\dfrac{1}2

59\dfrac{5}9

58\dfrac{5}8

Answer: B
Difficulty rating: 1580
Small Hint:

Look for a repeating 3×33\times3 block.

Big Hint:

In one block, combine pairs of half dark squares into whole dark squares.

Solution:

Notice that there are repeating 3×33 \times 3 regions with the same pattern (they might be rotated differently).

In this region, there are three dark unit squares and two dark triangles that combine to form another unit square.

This makes the area of the darker region 44 and the whole region 9.9. The desired fraction is then 49.\dfrac{4}{9}.

Thus, B is the correct answer.

24.

Miki has a dozen oranges of the same size and a dozen pears of the same size. Miki uses her juicer to extract 88 ounces of pear juice from 33 pears and 88 ounces of orange juice from 22 oranges. She makes a pear-orange juice blend from an equal number of pears and oranges. What percent of the blend is pear juice?

3030

4040

5050

6060

7070

Answer: B
Difficulty rating: 1610
Small Hint:

Use an equal convenient number of pears and oranges.

Big Hint:

Six pears and six oranges make both juice amounts easy to compute.

Solution:

Use 66 pears and 66 oranges, which is an equal number of each fruit.

Since 33 pears make 88 ounces, 66 pears make 1616 ounces. Since 22 oranges make 88 ounces, 66 oranges make 2424 ounces.

The blend has 16+24=4016+24=40 ounces total, of which 1616 ounces is pear juice. The pear-juice percent is 1640=40%.\frac{16}{40}=40\%.

Thus, B is the correct answer.

25.

Loki, Moe, Nick and Ott are good friends. Ott had no money, but the others did. Moe gave Ott one-fifth of his money, Loki gave Ott one-fourth of his money and Nick gave Ott one-third of his money. Each gave Ott the same amount of money. What fractional part of the group’s money does Ott now have?

110\dfrac{1}{10}

14\dfrac{1}{4}

13\dfrac{1}{3}

25\dfrac{2}{5}

12\dfrac{1}{2}

Answer: B
Difficulty rating: 1560
Small Hint:

Assume each friend gives Ott the same convenient amount.

Big Hint:

If each gives Ott $1,\$1, work backward to each friend’s original amount.

Solution:

Because only the fractions matter, suppose each person gave Ott $1.\$1. This means that Moe had $5,\$5, Loki had $4,\$4, and Nick had $3\$3 originally.

The transfers do not change the group’s total amount of money, which is $5+$4+$3=$12. \$5 + \$4 + \$3 = \$12. Ott now has $3.\$3.

This means that Ott has 312=14 \dfrac{3}{12} = \dfrac{1}{4} of the group’s money.

Thus, B is the correct answer.