Question
A was travelling from point X to point Y. He increased
his speed by 10 km/h after every hour. He reached his destination in 20 hours. If his initial speed was 25 km/h, then what was his average speed in the whole journey?Solution
Total distance travelled by A = (20/2) × {2 × 25 + (20 – 1) × 10} = 10 × (50 + 190) = 2400 km Required average speed = 2400/20 = 120 km/h
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