Question

Three bulbs red, green and yellow flash at intervals of 80 seconds, 90 seconds and 110 seconds. All
three flash together at 8:00 am. At what time will the three bulbs flash altogether again?

Answer 1

Answer:

The three bulbs flash altogether at 10:12 am

Solution:

Red bulb flashes at every 80 seconds

Green bulb flashes at every 90 seconds

Yellow bulb flashes at every 110 seconds

To know the time required fir three bulbs to flash together we need to find the LCM of 80,90 and 110

80=2×2×2×2×5

90=2×3×3×5

110=2×5×11

LCM = 2×5×2×2×2×3×3×11 = 7920

This means that at every 7920 seconds of interval three bulbs flash altogether

converting seconds into minutes we get as 132 minutes i.e., 2 hours 12 minutes

So three bulbs flash altogether at 10:12 am

Answer 2

Answer:

10:12am

Step-by-step explanation:

LCM of [80,90,110]=7920

Convert it into minute=7920/60

                                   =132min

New time=8:00+132min

               =10:12am