A mother is currently 4 times as old as her daughter. In 20 years, the mother will be twice as old as her daughter. How old is the daughter right now?
10 years old
Let D be the daughter's age. The mother's age is 4D. In 20 years, 4D + 20 = 2(D + 20). Simplifying yields 4D + 20 = 2D + 40, so 2D = 20, which means D = 10.
About this riddle
Math riddles hide a calculation inside a short story. Pull out the numbers, work out what is being asked, and watch for a trick such as a unit change.
Difficulty: Medium. More like this: Math riddles with answers or try Target 24 for a different kind of puzzle.
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