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| Math Central | Quandaries & Queries |
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Question from John, a student: Lisa is 15 years old. Marcus is 49 years old. How old will they both be when Marcus is three times as old as Lisa? |
Hi John.
You can use algebra to solve this puzzle.
Let Y = some number of years from now.
At that point in time, Lisa will be (15 + Y) years old and Marcus will by (49 + Y) years old.
That's when Marcus is three times as old as Lisa, so we know that
3 (15 + Y) = (49 + Y)
Does this help? Can you solve the problem now?
Stephen La Rocque.
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