Question
A cheetah can catch a deer running with a speed of 126
km/h and is 55 meters ahead of it, in 11 seconds. Find the time taken by the cheetah to catch a zebra that is 144 metres ahead of it and is running with a speed which is 80% of that of the deer.Solution
Speed of the deer = 126 km/h = 126 × (5/18) = 35 m/s Distance covered by the cheetah in 11 seconds = 55 metres + distance covered by the deer in 11 seconds = 55 + 35 × 11 = 55 + 385 = 440 metres So, speed of the cheetah = 440/11 = 40 m/s Speed of the zebra = 35 × (80/100) = 28 m/s So, relative speed of the cheetah with respect to the zebra = 40 – 28 = 12 m/s Hence, time taken by the cheetah to catch the zebra = 144/12 = 12 seconds
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