2016 AMC 8 Exam Solutions
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All of the real AMC 8 and AMC 10 problems in our complete solution collection are used with official permission of the Mathematical Association of America (MAA).
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1.
The longest professional tennis match ever played lasted a total of hours and minutes. How many minutes was this?
Solution:
There are minutes in an hour, so the total time is minutes.
Thus, C is the correct answer.
2.
In rectangle and Point is the midpoint of What is the area of
Solution:
From the diagram, we can see that the base of is and the altitude is The area is therefore
Thus, A is the correct answer.
3.
Four students take an exam. Three of their scores are and If the average of their four scores is then what is the remaining score?
Solution:
From the average, we can calculate the sum of the scores to be This means that the remaining score is
Thus, A is the correct answer.
4.
When Cheenu was a boy he could run miles in hours and minutes. As an old man he can now walk miles in hours. How many minutes longer does it take for him to walk a mile now compared to when he was a boy?
Solution:
To better compare the rates, we can change his speed into minutes per mile.
As a boy he ran miles in minutes, which means that he ran at a pace of minutes per mile.
As an adult, he can walk miles in minutes, which means he walks at a pace of minutes per mile.
Subtracting the two, we get that he takes more minutes to walk a mile as an adult.
Thus, B is the correct answer.
5.
The number is a two-digit number with the following properties:
• When is divided by the remainder is
• When is divided by the remainder is
What is the remainder when is divided by
Solution:
The two-digit numbers that leave a remainder of when divided by are: The two-digit numbers that leave a remainder of when divided by are: Among these numbers, is the only common number. The remainder of when divided by is
Thus, E is the correct answer.
6.
The following bar graph represents the length (in letters) of the names of 19 people. What is the median length of these names?
Solution:
Since there are people, each with one corresponding name length, the middle length will be the tenth one. Counting from the left side, the tenth value that we arrive upon is
Thus, B is the correct answer.
7.
Which of the following numbers is not a perfect square?
Solution:
Since any number with an even exponent is a perfect square, we can eliminate A, C, and E. Also, a square number to any power remains a square number, so that rules out D.
Thus, B is the correct answer.
8.
Find the value of the expression
Solution:
We can group the sum as follows: Note that each pair evaluates to and there are pairs. Therefore, the total sum is
Thus, C is the correct answer.
9.
What is the sum of the distinct prime integer divisors of
Solution:
We can prime factorize as This shows that the prime divisors of are and The sum of these is so B is the correct answer.
10.
Suppose that means What is the value of if
Solution:
We can simplify the equation as follows: Solving yields
Thus, D is the correct answer.
11.
Determine how many two-digit numbers satisfy the following property:
When the number is added to the number obtained by reversing its digits, the sum is
Solution:
Let be the two-digit number in question. Then, it follows that the number obtained by reversing its digits is Therefore, in order for to satisfy the property in the question: The only possible solutions to this equation, where are both one digit, are: As such, there are solutions.
Thus, B is the correct answer.
12.
Jefferson Middle School has the same number of boys and girls. Three-fourths of the girls and two-thirds of the boys went on a field trip. What fraction of the students on the field trip were girls?
Solution:
To more easily compare, we can convert the fractions to have the same denominator: This shows that the ratio of girls to boys is which means that the fraction of girls on the field trip is
Thus, B is the correct answer.
13.
Two different numbers are randomly selected from the set and multiplied together. What is the probability that the product is
Solution:
The only way for the product to be is if one of the number chosen is If the first number chosen is then there are options for the second number.
Similarly, there are combinations if was chosen second.
Therefore, there are total pairs where the product is The total number of pairs is so the probability is
Thus, D is the correct answer.
14.
Karl's car uses a gallon of gas every miles, and his gas tank holds gallons when it is full.
One day, Karl started with a full tank of gas, drove miles, bought gallons of gas, and continued driving to his destination. When he arrived, his gas tank was half full. How many miles did Karl drive that day?
Solution:
If Karl drove miles, then he used gallons of gas.
When he bought more gas, he added gallons to gallons, attaining a total of gallons.
If his tank was half full when he arrived, he used gallons, which equates to miles.
Therefore, he travelled a total distance of
Thus, A is the correct answer.
15.
What is the largest power of that is a divisor of
Solution:
We can factor this expression using difference of squares.
This shows that is the largest power of that divides the expression.
Thus, C is the correct answer.
16.
Annie and Bonnie are running laps around a -meter oval track. They started together, but Annie has pulled ahead, because she runs faster than Bonnie. How many laps will Annie have run when she first passes Bonnie?
Solution:
Since Annie is faster than Bonnie, for every lap Bonnie finishes, Annie completes laps. Therefore, Annie gains a quarter lap every time Bonnie finished a lap.
With this in mind, for Annie to completely lap Bonnie, Bonnie must finish laps, which means that Annie finished laps.
Thus, D is the correct answer.
17.
An ATM password at Fred's Bank is composed of four digits from to with repeated digits allowable. If no password may begin with the sequence then how many passwords are possible?
Solution:
The total number of passwords with no conditions is The condition removes possible passwords since the first are determined, and the last one can be anything. Therefore, the number of acceptable passwords is
Thus, D is the correct answer.
18.
In an All-Area track meet, sprinters enter a meter dash competition. The track has lanes, so only sprinters can compete at a time. At the end of each race, the five non-winners are eliminated, and the winner will compete again in a later race.
How many races are needed to determine the champion sprinter?
Solution:
Note that each race eliminates people. For there to be a winner, must be eliminated. Therefore, races are required to eliminate this number of people.
Thus, C is the correct answer.
19.
The sum of consecutive even integers is What is the largest of these consecutive integers?
Solution:
The average of these numbers is The largest number is even numbers away, which means that it equals
Thus, E is the correct answer.
20.
The least common multiple of and is and the least common multiple of and is What is the least possible value of the least common multiple of and
Solution:
We know that has to divide both and so it must equal either or
If then and making their least common multiple If then the smallest value of is and is The least common multiple in this scenario is
Thus, A is the correct answer.
21.
A top hat contains red chips and green chips. Chips are drawn randomly, one at a time without replacement, until all of the reds are drawn or until both green chips are drawn. What is the probability that the reds are drawn?
Solution:
The only way for the reds to be drawn first is if there is only one green drawn in the first draws. The green can be in any of the first spots, yielding possibilities.
We can find the total number of possibilities to be by listing them out. Therefore, the desired probability is
Thus, B is the correct answer.
22.
Rectangle below is a rectangle with The area of the "bat wings" (shaded area) is
Solution:
Define to be the midpoint of and to be the midpoint of Also define to be the intersection of and
The area of equals By symmetry, we can see that and are similar. Since their bases are in a ratio, so are their altitudes. This means that which implies that
Therefore, the area of This implies that the area of Since the figure is symmetric, the total area of the bat wings is
Thus, C is the correct answer.
23.
Two congruent circles centered at points and each pass through the other circle's center. The line containing both and is extended to intersect the circles at points and
The circles intersect at two points, one of which is What is the degree measure of
Solution:
We know that since they are all radii of congruent circles, so they form an equilateral triangle, which means that
Also, since and are diameters, Therefore, which equals
Thus, C is the correct answer.
24.
The digits and are each used once to write a five-digit number The three-digit number is divisible by the three-digit number is divisible by and the three-digit number is divisible by What is
Solution:
Since is divisible by we know that
Since is divisible by equals either or
This means that will equal either or Note that would require to be or each of which has solutions. Therefore the remaining digits when considering is the only number divisible by \(3.\
Therefore,
Thus, A is the correct answer.
25.
A semicircle is inscribed in an isosceles triangle with base and height so that the diameter of the semicircle is contained in the base of the triangle as shown. What is the radius of the semicircle?
Solution:
Let be the center of the circle, which is the midpoint of
We then get that via the Pythagorean theorem.
In addition, we can also calculate the area of as: As the area of we can see that
Thus, B is the correct answer.