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Question

A cheetah can catch a deer running with a speed of 36 km/h and is 45 meters ahead of it, in 12 seconds. Find the time taken by the cheetah to catch a zebra that is 135 metres ahead of it and is running with a speed which is 70% of that of the deer.

A 20 seconds Correct Answer Incorrect Answer
B 25 seconds Correct Answer Incorrect Answer
C 22 seconds Correct Answer Incorrect Answer
D 23 seconds Correct Answer Incorrect Answer
E None of these Correct Answer Incorrect Answer

Solution

Speed of the deer = 36 km/h = 36 × (5/18) = 10 m/s Distance covered by the cheetah in 12 seconds = 45 metres + distance covered by the deer in 12 seconds = 45 + 10 × 12 = 45 + 120 = 165 metres So, speed of the cheetah = 165/12 = 13.75 m/s Speed of the zebra = 10 × (70/100) = 7 m/s So, relative speed of the cheetah with respect to the zebra = 13.75 – 7 = 6.75 m/s Hence, time taken by the cheetah to catch the zebra = 135/6.75 = 20 seconds

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