John’s and Janice’s Age

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John is now 10 years older than Janice. If 10 years ago John was twice as old as Janice, how old will John be in 5 years?

Review: John's and Janice's Age


Explanation

In this question, the algebra translation commonly causes errors, but we can confirm the correct answer by walking it through the described scenario. If John's age is J and Janice's age is N, then



and







Substituting J:





And, plugging back into our topmost equation, . We confirm, 10 years ago, John was 20 and Janice was 10, so he was twice her age. We want John's age in 5 years, which is 35.

The correct answer is (E).


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