A girl is twice as old as her sister. Five years hence, the product of their ages (in years) will be 375. Find their present age

Question

3 years ago

12

s. A girl is twice as old as her sister. Five years hence, the product of their ages (in years) will be 375. Find their present ages.

1 answer:

Orlov [11] · Answer 1 · 2022-05-11T11:39:12+03:00

Answer: girls=20, sister=10

Step-by-step explanation:

Let x = the girl's sister's age (present)

Let 2x= the girl's age (present)

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According to the question

(x+5)(2x+5)=375

Expand parentheses by FOIL (First Outer Inner Last)

2x²+5x+10x+25=375

Combine like term (5x and 10x)

2x²+15x+25=375

Subtract 375 on both sides

2x²+15x+25-375=375-375

2x²+15x-350=0

Find the factors (cross factor)

(x-10)(x+17.5)=0

x=10 or x=-17.5 (rej) ⇔ the age can't be negative

the girl's age is 20, and her sister's age is 10.