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

Three bells toll at intervals of 12, 10, 2 minutes. If they toll together now, after how many minutes will they next toll together?

Find the L.C.M. of 30, 16 and 4.

Find the L.C.M. of 38, 4 and 7.

What is the least number which, when divided by 10, 8, 20, leaves a remainder 2 in each case?

What is the least number which, when divided by 8, 20, 5, leaves a remainder 2 in each case?