Homework Help: Kathie

Posted by Mathematics on Wednesday, January 11, 2012 at 8:35am.

In four years' time, a father will be three times as old as his son. Six years ago, he was seven times as old as his son. How old are they now? Explain your workings. Thanks

Kathie - Reiny, Wednesday, January 11, 2012 at 8:50am
son's present age: x
father's present age : y

4 yrs from now:
son : x+4
father : y+4
y+4 = 3(x+4)
y = 3x + 8

6 yrs ago:
son : x-6
father: y-6
y - 6 = 7(x-6)
y = 7x -36

so 7x -36 =3x+8
4x = 44
x = 11
y = 3(11)+8 = 41

The son is now 11 and the father is now 41

check:
4 yrs from now: son-- 15, father 45
3 times as old? yes

6 yrs ago: son -- 5, father 35
7 times as old? yes

all is good
Kathie - Mathematics, Wednesday, January 11, 2012 at 10:01am
Thank you very much Reiny!

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