A completes a lap in 40 seconds and B in 56 seconds. They start together from the starting point. After how many seconds are they next at the starting point together?

96 secondsCorrect answerYour answer140 secondsCorrect answerYour answer280 secondsCorrect answerYour answer2,240 secondsCorrect answerYour answer

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CorrectNot quiteAnswer C

Correct answer: C

Each is at the start after a whole number of its laps: A at multiples of 40, B at multiples of 56.
The first common time is $\text{LCM}(40, 56) = 280$ seconds.

Worth noting

2,240 is $40 \times 56$ , a common multiple but not the least.

Ten questions from Races & Games, at your own pace.

Explanation