Math CentralQuandaries & Queries


Question from Lemicio:

Janet is 10 years older than Karin, who is twice the age of Josef. If their combine age is 55, how old is each one now?

Hi Lemicio,

Suppose J is Janet's age, K is Karin's age and S is Joseph's age. Since Janet is 10 years older than Karin we know that

\[J = K + 10\]

This is the first equation in K and J.

We also know that Karin is twice the age of Josef. This gives a second equation in K and S.

We also have a third equation that says that the sum of their ages is 55.

Solve the third equation for S. Substitute this and the first equation into the third equation and solve for K.


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