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When Will the Father Be Exactly Twice His Son's Age?
A father is 40 years old and his son is 10. In how many years will the father's age be exactly twice the son's age?
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What is the answer to the father and son age riddle?
In 20 years. The father will be 60 and the son will be 30, so the father is exactly twice the son's age.
How do you solve the 'twice as old' age riddle?
Let x be the number of years. Solve 40 + x = 2 × (10 + x), which expands to 40 + x = 20 + 2x. So x = 20 years.
Why isn't the answer 10 or 30 years?
The gap between their ages is always 30 years. The father is twice as old only when the son reaches 30, which happens in 20 years, not 10 or 30.