Difference between revisions of "2015 AMC 10A Problems/Problem 8"
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Two years ago Pete was three times as old as his cousin Claire. Two years before that, Pete was four times as old as Claire. In how many years will the ratio of their ages be 2 : 1 ? | Two years ago Pete was three times as old as his cousin Claire. Two years before that, Pete was four times as old as Claire. In how many years will the ratio of their ages be 2 : 1 ? | ||
| − | <math> \textbf{( | + | <math> \textbf{(A)}\ 2 \qquad\textbf{(B)} \ 4 \qquad\textbf{(C)} \ 5 \qquad\textbf{(D)} \ 6 \qquad\textbf{(E)} \ 8 </math> |
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==Solution== | ==Solution== | ||
Revision as of 15:58, 4 February 2015
Problem
Two years ago Pete was three times as old as his cousin Claire. Two years before that, Pete was four times as old as Claire. In how many years will the ratio of their ages be 2 : 1 ?
Solution
This problem can be converted to a system of equations. Let 
be Pete's current age and 
be Claire's current age.
The first statement can be written as 
. The second statement can be written as 
To solve the system of equations:
Let 
be the number of years until Pete is twice as old as Claire.
The answer is 
.
