Question

four watches are ringing alarm bells in the interval of 6, 12,15,18 seconds. if they start at the same time , how many times they will ring together in 4 hours?

Answer 1

Answer:

81

Step-by-step explanation:

Hi,

To calculate this, we should consider the L.C.M of 6, 12, 15 and 18.

L.C.M of 6, 12, 15, 18 is 180

Hence, the watches will ring simultaneously after every 180 sec i.e.,

after every 3 minutes.

In 4 hours ( 4 * 60 = 240 minutes), the watches will ring simultaneously

for 80 times.

Including the simultaneous ring at the start, the watches will ring

simultaneously for 81 times.

Hope, it helped !

Answer 2

Answer:

81 times

Step-by-step explanation:

Find the LCM:

6 = 2 x 3

12 = 2² x 3

15 = 3 x 5

18 = 2 x 3²

LCM = 2² x 3² x 5 = 180 seconds

Convert 4 hours to seconds:

4 hours = 4 x 60 mins = 240 mins

240 mins = 240 x 60 sec = 14400 seconds

Find the number of times:

Number of times = (14400 ÷ 180) + 1 = 81

Answer; It will ring 81 times.