Question 1072161: Ellie is twice as old as her sister kate. In seven years the sum of their ages will be 20. How old are they now?
Answer by math_helper(2461)   (Show Source):
You can put this solution on YOUR website! Ellie is twice as old as her sister kate. In seven years the sum of their ages will be 20. How old are they now?
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Let E = Ellie's age
and K = Kate's age
E = 2K (1)
(E+7)+ (K+7) = 20 (2)
Substitute 2K for E from (1), into (2):
(2K+7) + (K+7) = 20
3K + 14 = 20
3K = 6
K = 2 —> E = 2K = 2*2 = 4
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Ans: Kate is 2 years old, Ellie is 4 years old
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Check: in 7 years, Kate will be 9 and Ellie will be 11, and 9+11 = 20, so that check ok.
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