Question

Ardem has two lights one flashes every 15 seconds, the other flashes every 42 seconds they start flashing at the same time. After how many seconds will they take next flash at the same time

Answer 1

210 seconds

Explanation:

To find out when both lights will flash at the same time again, we need to find the least common multiple (LCM) of their flash intervals.

The flash intervals are 15 seconds and 42 seconds.

1. List the multiples

- Multiples of 15: 15, 30, 45, 60, 75, 90, ...

- Multiples of 42: 42, 84, 126, 168, ...

2. Identify the common multiples

- The first common multiple is 42.

- The second common multiple is 84.

3. LCM

- The LCM of 15 and 42 is 210.

So, after 210 seconds, both lights will flash at the same time again. This is because 210 seconds is the least common multiple of 15 seconds and 42 seconds.