Question

in a school , the 1st bell rings after every 30 minutes for primary section , the second bell rings after every 40minutes for middle section and the third bell rings after every 45 minutes for senior section . if the school starts at 9 am with a bell for all these sections then when will the the three bells ring together again after 9 AM​

Answer 1

Answer:

11 a.m

Step-by-step explanation:

L.C.M of 30,40,45 are:

30= 2 * 3 * 5

40= 2^3 * 5

45= 3^2 * 5

therfore, l.c.m= 2^3 * 3 * 5

                      = 120

i.e, the next Bell will ring after 120 minutes which is 2 hours.

Therfore, required answer= 9 a.m + 2 hours= 11 a.m.