Three sisters are all three years apart in age. If you sum their ages together you get 18. How old is the youngest sister?

Question

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Answer 1

3

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A = the eldest, B = the midle, C = the young

A + B + C = 18

C - B = 3

B - A = 3

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B = 18 ÷ 3 = 6

A = 6 - 3

A = 3

Answer 2

If y is the youngest age, then the other two are y+3 and y+6, so their total is 3y+9=18.

3y=9, so y, the youngest age is 3. (The other two are aged 6 and 9.)

Answer 3

Let their age be (x-3), x and (x+3).

Given, (x-3) + x + (x+3) =18

=> 3x = 18

=> x= 6

So the age of youngest sister is (x-3) = 6-3 = 3 years