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Question:

Shruti and Krishna left Delhi for Noida at the same time. While Shruti was driving her car, Krishna, an environmentalist by profession, was traveling on his bicycle. Having reached Noida, Shruti turned back and met Krishna an hour after they started. Krishna continued his journey to Noida after the meeting, while Shruti turned back and also headed for Noida. Having reached Noida, Shruti again turned back and met Krishna 30 minutes after their first meeting. The time taken by Krishna to cover the distance between Delhi and Noida is

Explanation:

Shruti and Krishna leave for the first time. Their first meeting is after one hour, the second is after an additional half an hour.
So, the interval between subsequent meetings keeps halving every time.

∴ Total time = 60 + 30 + 15 + ….

This is an infinite G.P. with a = 60 and r = 1/2

∴ Sum of terms = a / (1 – r) = 60 /[1 – (1/2)] = 120 minutes = 2 hours

Hence, option (a).

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