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Three wheels rotate around the same horizontal axis, completing 15, 20, and 48 revolutions per minute respectively. If they all start from the same point on their circumference facing downward, after how much time will they align again at that exact position?

Problems on L.C.M and H.C.F MCQs for PPSC, FPSC, NTS, and Pakistan government job tests. Select an option below, then read the explanation.

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Problems on L.C.M and H.C.Fmathematics-mcqs › problems-on-l-c-m-and-h-c-f
Published
12 Jul 2019
Last updated
28 May 2026

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Explanation

The time for one complete revolution for each wheel is calculated as 60 divided by their revolutions per minute: 60/15 = 4 seconds, 60/20 = 3 seconds, and 60/48 = 1.25 seconds. To find when they all align again, we determine the least common multiple (LCM) of these times. Converting to fractions: 4, 3, and 5/4 seconds. The LCM of these values is 60 seconds, which equals 1 minute. Therefore, all wheels will simultaneously return to the starting position after 1 minute.

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