SOLUTION: in two yrs a boy will be 3/4 as old as his sister.
two yrs ago he was 2/3 as old as she. how old are they?
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Question 628531: in two yrs a boy will be 3/4 as old as his sister.
two yrs ago he was 2/3 as old as she. how old are they?
Answer by ankor@dixie-net.com(22740) (Show Source): You can put this solution on YOUR website!
b = boy's present age
s = sister's present age
:
"in two yrs a boy will be 3/4 as old as his sister."
b + 2 = (s+2)
multiply by 4 to get rid of the fraction
4(b+2) = 3(s+2)
4b + 8 = 3s + 6
4b = 3s + 6 - 8
4b = 3s - 2
4b - 3s = -2
:
"two yrs ago he was 2/3 as old as she."
b - 2 = (s-2)
multiply by 3
3(b-2) = 2(s-2)
3b - 6 = 2s - 4
3b = 2s - 4 + 6
3b - 2s = 2
:
Let use elimination here, multiply 1st equation by 2, the 2nd eq by 3
8b - 6s = -4
9b - 6s = 6
--------------subtraction eliminates s, find b
-b = -10
b = 10 yrs is the boys present age
:
Find s: 3b - 2s = 2
3(10) - 2s = 2
30 - 2 = 2s
28 = 2s
s = 28/2
s = 14 yrs is the sister's present age
:
You can check these solutions in the given statements.
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