Question
The average weight of 5 people increases by 2 kg if a
new person replaces one weighing 60 kg. What is the weight of the new person?Solution
Let average weight of 5 men be x, then Sum of weight of 5 men = 5x If a man replaced, then average weight of 5men = (x + 2) If a man replaced, then sum of weight of 5men = 5 (x + 2) = 5x + 10 Let weight of new man be y, then According to the question 5x – 60 + y = 5x + 10 ⇒ y = 5x + 10 + 60 – 5x ∴ y = 70 Short Trick: Weight of new man = increase weight × number of persons + weight of replace man ∴ Weight of new man = 2 × 5 + 60 = 70 kg
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