### Brain Teasers

# Twice As Old

A girl is twice as old as her brother and half as old as her father. In 22 years, her brother will be half as old as his father. How old is the daughter now?

### Answer

She is 22. Her brother is 11 and her father is 44. In 22 years, her brother would be 33 and their father would 66.Hide Answer Show Answer

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## Comments

this is a simple teaser tt can be solved using algebra!

Let:

F = father's current age

B = brother's current age

G = girl's current age

Given:

G = 2B = 0.5F

=> 2G = 4B = F

In 22 years,

Brother's age = 0.5 (Father's age)

Therefore,

(F+22)/2 - B = 22

=> F = 22 + 2B

Substitute 4B = F to F = 22 + 2B,

4B = 22 + 2B

=> B = 11

Answer: Girl is 22.

F = father's current age

B = brother's current age

G = girl's current age

Given:

G = 2B = 0.5F

=> 2G = 4B = F

In 22 years,

Brother's age = 0.5 (Father's age)

Therefore,

(F+22)/2 - B = 22

=> F = 22 + 2B

Substitute 4B = F to F = 22 + 2B,

4B = 22 + 2B

=> B = 11

Answer: Girl is 22.

No algebra needed, just a little logic.

If the son is one quarter as old as the dad, then he needs to double his age to be half as old. During that same time he also needs to keep pace with half the rate his dad is getting older at, which is half of 22. That means the other half of twenty two is what he needs to be half his dad's age today, which also happens to be his age.

If the son is one quarter as old as the dad, then he needs to double his age to be half as old. During that same time he also needs to keep pace with half the rate his dad is getting older at, which is half of 22. That means the other half of twenty two is what he needs to be half his dad's age today, which also happens to be his age.

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