Question

Spotlight A changes color every 60 seconds spotlight B changes color every 90 seconds.Both spotlights changed.After how many seconds will the spotlights change color at the same time again

Answer 1

They will change color at the same time in the next 180 seconds or 3 minutes

Explanation:

Here, we have two spotlights which change colors at intervals.

While one changes every 60 seconds, the other changes every 90 seconds. Now, we are concerned with knowing when they will both change colors at the same time or instant.

The key to solving this is straightforward. What we need to do is to find the lowest common multiple of both numbers i.e 60 and 90.

The lowest common multiple of both is 180 seconds. This means in the next three minutes, both spotlights will change color at the same time.

Let’s take this by counting;

Spotlight A; 60 , 120 , 180

Spotlight B: 90 , 180