### Brain Teasers

# All In The Family

Joe's dad is three times older than Joe. Joe's grandfather is twice as old as Joe's dad. The sum of all their ages is 100. How old are Joe, his dad, and his grandfather?

### Answer

Joe is 10, his father is 30, and his grandfather is 60.Set up the equations:

D = 3 * J

G = 2 * D

J + D + G = 100

Solve these to get the answer.

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## Comments

Nice little puzzle. If you just use one variable then Jo is x yrs old, Dad is 3x yrs old and Granpa is 6x yrs old. 6x+3x+x=100. 10=100. x=10. Etc.

Simple and sweet. Thanks for the teaser.

This one needs a more explanatory answer.

These proportional teaers are very easy if you just translate the proportions to ratios (parts) and then divide by the number of parts to get the value of one part.

The ratio is 1:3:6. 1+3+6=10 parts. 100/10 = 10 for each part. 10, 30, 60. This problem shouldn't take anyone more than ten seconds to do in their head once you know how to do it. Few of the other teasers in this style should take any longer.

The ratio is 1:3:6. 1+3+6=10 parts. 100/10 = 10 for each part. 10, 30, 60. This problem shouldn't take anyone more than ten seconds to do in their head once you know how to do it. Few of the other teasers in this style should take any longer.

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