SOLUTION: sally is four years older than helen. the product of there ages is 45, how old is sally?

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Question 627043: sally is four years older than helen. the product of there ages is 45, how old is sally?
Answer by Maths68(1474) About Me  (Show Source):
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Let
Present age of Sally = s years old
Present age of Helen = h years old


Sally is four years older than Helen
s=h+4...........(1)
The Product of their ages is 45
s*h=45...........(2)
Substitute the value of s from (1) to (2)
(h+4)*h=45
h^2+4h=45
h^2+4h-45=0
Now Solve for h
h^2+9h-5h-45=0
h(h+9)-5(h+9)=0
(h-5)(h+9)=0
h-5=0 or h+9=0
h=5 or h=-9 (inadmissible)
so
h=5
Put the value of 5 in (1)
s=h+4...........(1)
s=5+4
s=9


Present age of Sally = s = 9 years old
Present age of Helen = h = 5 years old