Jun Heng's answer to The best one's Secondary 2 Maths Singapore question.
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Let age of Ana be a and age of Bonita be b
b+n = a → (1)
5(b–1) = a–1 → (2)
a = b² → (3)
Sub (3) into (2)
5(b–1) = b²–1
5b–5 = b²–1
b²–5b+4 = 0
(b–1)(b–4) = 0
b = 1 (rej since b > 1) or b = 4
Sub b = 4 into (3)
a = 4² = 16
Sub a = 16 and b = 4 into (1)
4+n = 16
n = 12
b+n = a → (1)
5(b–1) = a–1 → (2)
a = b² → (3)
Sub (3) into (2)
5(b–1) = b²–1
5b–5 = b²–1
b²–5b+4 = 0
(b–1)(b–4) = 0
b = 1 (rej since b > 1) or b = 4
Sub b = 4 into (3)
a = 4² = 16
Sub a = 16 and b = 4 into (1)
4+n = 16
n = 12
Date Posted:
1 year ago
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