Large family

The average age of all family members (children, mother, father, grandmother, grandfather) is 29 years. The average age of parents is 40 years, grandparents 66 years, and all children are five years. How many children are there in this family?

Correct answer:

n =  4

Step-by-step explanation:

$$\begin{gathered} 29\cdot (n+2+2)=5n+2\cdot 40+2\cdot 66 \\ 29\cdot (n+2+2)=5\cdot n+2\cdot 40+2\cdot 66 \\ 24n=96 \\ n=\frac{96}{24}=4 \\ n=4 \end{gathered}$$

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