Question

In a school, duration of a period in primary section is 40 minutes and that of the
secondary section is 45 minutes. If the bell for each section rings at 7 a.m., when will the
two bells ring together again?​

Answer 1

Answer:

Step-by-step explanation:

you have to find out the LCM of 40 and 45

which is 360 min

= 6hrs hence the will ring together at 7+6 =1 pm

Answer 2

Answer:

Both the bell will ring at 1 P.M.

Step-by-step explanation:

To find when the two bells ring together again, we have to find out L.C.M of 40 and 45

Therefore,  

L.C.M of 40 and 45  

            40 = 2 × 2 × 2 × 5

            45 = 3 × 3 × 5

L.C.M = 23 × 32 × 5

    = 8 × 9 × 5

    = 360 min

Hence, the both the bell will ring together after 6 hours means at 1p.m.