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There are 3 pendulums in the science lab room. The first pendulum swings back and forth every 6 seconds.
The second pendulum swings back and forth for 5 seconds, the third pendulum swings back and forth every 3 seconds.
If they all started at the same time, every how many seconds will they have the same starting point ?
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This problem is about Less Common Multiple (LCM) of the numbers 6, 5 and 3.
The LCM is 30.
Answer. In 30 seconds.