Question
A is cycling at an average speed of 20 km/hr such that
he can reach a certain point at 12 noon. If he cycles at 60 km/hr, then he will reach the destination at 10 a.m. At what speed he should cycle to reach the destination at 11 a.m.Solution
Let the distance to be travelled be ‘x’ km Time taken when speed is 20 km/hr = (x/20) hours Time taken when speed is 60 km/hr = (x/60) hours According to the question, (x/20) – (x/60) = 2 Or, 3x – x = 2 × 60 Or, 2x = 120 km Or, x = 60 km Time taken to travel 60 km with speed of 20 km/hr = 60/20 = 3 hours Therefore, he started at 12 – 3 = 9 a.m. Therefore, required speed to reach the destination at 11 a.m. or 2 hours = 60/2 = 30 km/hr
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