Question

An electronic device makes a beep after every 15 minutes. Another device makes a beep after every 20 minutes. They beeped together at 6 a.m. At what time they will next beep together?

Answer 1

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Answer 2

Here,

$15 = 3 \times 5 \\ 20 = 2 \times 2 \times 5$

So,

• LCM(15, 20) = 3 × 2 × 2 × 5 = 60

As LCM of 15 (minutes) and 20 (minutes) is 60 (minutes), thus, the devices would beep after 60 minutes i.e. 1 hour, or at 7 A.M