The sum of the ages of 6 children born at the interval of two years each is 90 years. What is the age (in years) of the eldest child?

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Accepted Answer

Let the age of the youngest child be x years. Since each child is born at an interval of 2 years, the ages of the 6 children will be: x, x+2, x+4, x+6, x+8, x+10.

Sum of their ages = x + (x+2) + (x+4) + (x+6) + (x+8) + (x+10) = 90

Combine like terms:
6x + (2 + 4 + 6 + 8 + 10) = 90  
6x + 30 = 90

Subtract 30 from both sides:    
6x = 60

Divide both sides by 6:  
x = 10

The youngest child is 10 years old.

The eldest child is x + 10 = 10 + 10 = 20 years old.

Therefore, the age of the eldest child is 20 years.

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