Question

The difference of the ages of a sister and her younger brother is 6 years. The

numerical value of the product of their ages is equal 4 times the sum of their
Find the present ages of the sister and her brother.
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Answer 1

bother = 6 years ; sister = 12 years

Explanation:

s = sister

b = brother

s - b = 6

s * b = 4(s+b)

s = b + 6

b(b+6) = 4(b+6 + b)

b² + 6b = 4(2b + 6)

b² + 6b = 8b + 24

b² + 6b - 8b - 24 = 0

b² - 2b - 24 = 0

(b-6)(b+4) = 0

b = 6

b = -4 (impossible because an age can’t be negative)

s = 6 + 6

s = 12