SOLUTION: A boy is 4 years old and his sister is three times as old as he is. When the boy is 12 years old, how old will his sister be?

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Question 52521: A boy is 4 years old and his sister is three times as old as he is. When the boy is 12 years old, how old will his sister be?
Answer by darq(90) About Me  (Show Source):
You can put this solution on YOUR website!
if boy is x years old than her sister is 3x years old.
x=4
3x=3*4=12

to find how many years had passed away when he became 12 subtract his current age from 12.

12-4=8

if 8 years had passed add 8 years to sister's current age to find the answer.

12+8=20 is the answer