How Old is Sarah?

Algebra Level 2

Sarah went to get her driver's licence. When asked her age, she replied: My age today is three times what it will be three years from now minus three time what my age was three years ago." How old is Sarah?

10 Years old 18 Years old 12 Years old 15 Years old

Lim Xiangying by Lim Xiangying , 21, Singapore

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4 solutions

Lim Xiangying
Dec 29, 2017

If she is 18, then three times her age three years from now would be 21 3 (63). 3 times her age 3 years ago would be 15 3(45). Subtract 45 from 63 and she is 18.

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logically, a little kid can not get a driver's license lmao

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If T is her age today, then her age 3 years from now is T+3 and her age 3 years ago was T-3. So we have the equation

T=3(T+3)-3(T-3)

Simplifying further, we have

T=3T+9-3T+9

T=18 (answer)

0 Helpful 0 Interesting 1 Brilliant 0 Confused
Eric Scholz
Jul 24, 2019

We can ignore the absolute value of her future and past age, all that mattes is the difference. 3times 3years in both directions, her age is the sum of both differences -> 2 * 3 * 3=18

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