The sum of ages of man and his son is 45 years. 5 years ago the product of their ages was 4 times the man's age at that time. find their present ages.
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LET AT PRESENT, MAN'S AGE=M AND SON'S AGE=S
I.E. M+S=45 I.E. M=45-S.................1
ALSO (M-5)(S-5)=4(M-5)
I.E. MS-9M-5S+45=0.............................2
BY PUTTING THE VALUE OF M FROM 1 IN 2, WE GET
S^2-49S+360=0
I.E. EITHER S=40 OR S=9
BY TAKING S=40 IN 1, WE GET M=45-40=5, WHICH IS NOT POSSIBLE
BY TAKING S=9 IN 1, WE GET M=45-9=36, WHICH IS POSSIBLE
I.E MAN'S AGE=36 AND SON'S AGE=9
I.E. M+S=45 I.E. M=45-S.................1
ALSO (M-5)(S-5)=4(M-5)
I.E. MS-9M-5S+45=0.............................2
BY PUTTING THE VALUE OF M FROM 1 IN 2, WE GET
S^2-49S+360=0
I.E. EITHER S=40 OR S=9
BY TAKING S=40 IN 1, WE GET M=45-40=5, WHICH IS NOT POSSIBLE
BY TAKING S=9 IN 1, WE GET M=45-9=36, WHICH IS POSSIBLE
I.E MAN'S AGE=36 AND SON'S AGE=9
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