Problems on H.C.F and L.C.M - General Questions

The H.C.F. of two numbers is 4 and their L.C.M. is 40. If one of the numbers is 8, what is the other?

Three bells toll at intervals of 3, 9, 2 minutes. If they toll together now, after how many minutes will they next toll together?

Find the H.C.F. of 36, 96 and 48.

Find the L.C.M. of 5, 31 and 26.

Find the H.C.F. of 42, 36 and 18.