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1985 AJHSME Problems/Problem 5

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Problem

unitsize(13);draw((0,0)--(20,0));draw((0,0)--(0,15));draw((0,3)--(-1,3));draw((0,6)--(-1,6));draw((0,9)--(-1,9));draw((0,12)-...

The bar graph shows the grades in a mathematics class for the last grading period. If A, B, C, and D are satisfactory grades, what fraction of the grades shown in the graph are satisfactory?

\text{(A)}\ \frac{1}{2} \qquad \text{(B)}\ \frac{2}{3} \qquad \text{(C)}\ \frac{3}{4} \qquad \text{(D)}\ \frac{4}{5} \qquad \...

Solution

To get the fraction, we need to find the number of people who got grades that are "satisfactory" over the total number of people.

Finding the number of people who got acceptable grades is pretty easy. 5 people got A's, 4 people got B's, 3 people got C's and 3 people got D's. Adding this up, we just have 5+4+3+3 = 15.

So we know the top of the fraction is 15. Only 5 people got "unacceptable" scores, so there are 15 + 5 = 20 scores.

\frac{15}{20}=\frac{3}{4} is our fraction, so \boxed{\text{C}} is the answer.

See Also

1985 AJHSME (ProblemsResources)
Preceded by
Problem 4
Followed by
Problem 6
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Want to learn how to tackle those tough AMC/AIME/Olympiad algebra problems? Check out Art of Problem Solving's Intermediate Algebra by Richard Rusczyk and Mathew Crawford. Over 1600 problems!
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