Hi,

The oldest child in a family of four children is twice as old as the youngest. The two middle children are 12 and 16 years old. 

If the average age of the children is 13.75, how old is the youngest child?

Let x be the youngest child's age & 2x the oldest child's age:

Write as You Read:

(2x + 12 + 16 + x)/4 = 13.75 'average' = sum of ages divided by 4

 3x + 28 = 55

 3x = 27

x = 9 the youngest child's age

Checking our Work:

 (18 + 12 + 16 + 9) / 4 = 13.75  checks

Wish You the Best in your Studies. 

Answer by josgarithmetic(39617)   (Show Source): You can put this solution on YOUR website!
 
YOUNGEST             j
MIDDLE Low          12
MIDDLE High         16
OLDEST              2j
Average            13.75


You see what to do? 

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