1958 AMC 12 Problem 45

Attempt Problem 45 of the 1958 AMC 12 below, then check your answer against the professionally curated solution from LIVE by Po-Shen Loh. You can also try the full timed exam, view all 1958 AMC 12 solutions, or check the answer key.

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

45.

A check is written for xx dollars and yy cents, xx and yy both two-digit numbers. In error it is cashed for yy dollars and xx cents, the incorrect amount exceeding the correct amount by $17.82.\$17.82. Then:

xx cannot exceed 7070

yy can equal 2x2x

the amount of the check cannot be a multiple of 55

the incorrect amount can equal twice the correct amount

the sum of the digits of the correct amount is divisible by 99

Answer: B
Concepts:moneydigitslinear equation
Difficulty rating: 1790
Small Hint:

Write the correct and incorrect amounts in cents

Big Hint:

Their difference simplifies to 99(yx)99(y-x)

Solution:

In cents, the incorrect amount minus the correct amount is (100y+x)(100x+y)=99(yx). \begin{aligned} &(100y+x)-(100x+y)\\ &\qquad=99(y-x). \end{aligned} Since $17.82\$17.82 is 17821782 cents, 99(yx)=1782, 99(y-x)=1782, so yx=18.y-x=18. The two-digit values x=18, y=36x=18,\ y=36 satisfy this relation and have y=2x.y=2x. Thus that equality can occur.

Therefore, the correct answer is B.

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Problem 45 in Other Years

1950 AMC 12 · 1951 AMC 12 · 1952 AMC 12 · 1953 AMC 12 · 1954 AMC 12 · 1955 AMC 12 · 1956 AMC 12 · 1957 AMC 12 · 1959 AMC 12