Art of Problem Solving

1986 AJHSME Problems/Problem 12: Difference between revisions

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==Solution==
==Solution==


This is just a lot of adding. We just need to find the number of those who DID get the same on both tests, over ([[fraction]]-wise) the number of students who took both tests, TOTAL, regardless of whether they got the same or not.
We need to find the number of those who did get the same on both tests over 30 (the number of students in the class).


So, we have <cmath>\frac{2 + 4 + 5 + 1}{2 + 2 + 1 + 0 + 0 + 1 + 4 + 3 + 0 + 0 + 1 + 3 + 5 + 2 + 0 + 0 + 0 + 1 + 1 + 1 + 0 + 0 + 2 + 1 + 0}</cmath>
So, we have <cmath>\frac{2 + 4 + 5 + 1}{30}</cmath>


Which simplifies to <cmath>\frac{12}{30} = \frac{4}{10} = \frac{40}{100} = 40 \%</cmath>
Which simplifies to <cmath>\frac{12}{30} = \frac{4}{10} = \frac{40}{100} = 40 \%</cmath>


<math>\boxed{\text{D}}</math>
<math>\boxed{\text{D}}</math>
''Note: As the problem tells us there are 30 students, the denominator calculation was unnecessary''


==See Also==
==See Also==

Revision as of 20:14, 8 October 2012

Problem

The table below displays the grade distribution of the $30$ students in a mathematics class on the last two tests. For example, exactly one student received a 'D' on Test 1 and a 'C' on Test 2 (see circled entry). What percent of the students received the same grade on both tests?

[asy] draw((2,0)--(7,0)--(7,5)--(2,5)--cycle); draw((3,0)--(3,5)); draw((4,0)--(4,5)); draw((5,0)--(5,5)); draw((6,0)--(6,5)); draw((2,1)--(7,1)); draw((2,2)--(7,2)); draw((2,3)--(7,3)); draw((2,4)--(7,4)); draw((.2,6.8)--(1.8,5.2)); draw(circle((4.5,1.5),.5),linewidth(.6 mm)); label("0",(2.5,.2),N); label("0",(3.5,.2),N); label("2",(4.5,.2),N); label("1",(5.5,.2),N); label("0",(6.5,.2),N); label("0",(2.5,1.2),N); label("0",(3.5,1.2),N); label("1",(4.5,1.2),N); label("1",(5.5,1.2),N); label("1",(6.5,1.2),N); label("1",(2.5,2.2),N); label("3",(3.5,2.2),N); label("5",(4.5,2.2),N); label("2",(5.5,2.2),N); label("0",(6.5,2.2),N); label("1",(2.5,3.2),N); label("4",(3.5,3.2),N); label("3",(4.5,3.2),N); label("0",(5.5,3.2),N); label("0",(6.5,3.2),N); label("2",(2.5,4.2),N); label("2",(3.5,4.2),N); label("1",(4.5,4.2),N); label("0",(5.5,4.2),N); label("0",(6.5,4.2),N); label("F",(1.5,.2),N); label("D",(1.5,1.2),N); label("C",(1.5,2.2),N); label("B",(1.5,3.2),N); label("A",(1.5,4.2),N); label("A",(2.5,5.2),N); label("B",(3.5,5.2),N); label("C",(4.5,5.2),N); label("D",(5.5,5.2),N); label("F",(6.5,5.2),N); label("Test 1",(-.5,5.2),N); label("Test 2",(2.6,6),N); [/asy]

$\text{(A)}\ 12\% \qquad \text{(B)}\ 25\% \qquad \text{(C)}\ 33\frac{1}{3}\% \qquad \text{(D)}\ 40\% \qquad \text{(E)}\ 50\%$

Solution

We need to find the number of those who did get the same on both tests over 30 (the number of students in the class).

So, we have \[\frac{2 + 4 + 5 + 1}{30}\]

Which simplifies to \[\frac{12}{30} = \frac{4}{10} = \frac{40}{100} = 40 \%\]

$\boxed{\text{D}}$

See Also

1986 AJHSME (ProblemsAnswer KeyResources)
Preceded by
Problem 11
Followed by
Problem 13
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
All AJHSME/AMC 8 Problems and Solutions