1971 AMC 12 Problem 4

Attempt Problem 4 of the 1971 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 1971 AMC 12 solutions, or check the answer key.

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

After simple interest for two months at

5\%

per annum was credited, a Boy Scout Troop had a total of

\$255.31

in the Council Treasury. The interest credited was a number of dollars plus the following number of cents:

11

12

13

21

31

Two months is one-sixth of a year

P

is the principal, solve

255.31=P(1+\frac{0.05}{6})

P

is the principal, then

\begin{aligned} 255.31&=P\left(1+\frac{0.05}{6}\right)\\ &=P\frac{121}{120}. \end{aligned}

Hence

P=253.20,

so the interest is

\$2.11

and its cents part is

11.

Therefore, the correct answer is A.

Problem 4 in other years