Question
A was travelling from point X to point Y. He increased
his speed by 14 km/h after every hour. He reached his destination in 18 hours. If his initial speed was 20 km/h, then what was his average speed in the whole journey?Solution
Total distance travelled by A = (18/2) × {2 × 20 + (18 – 1) × 14} = 14 × (40 + 238) = 2502 km Required average speed = 2502/18 = 139 km/h
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