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

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

Find the greatest number that divides 64, 204, 84 leaving the same remainder in each case.

Three bells toll at intervals of 12, 4, 5 minutes. If they toll together now, after how many minutes will they next toll together?

Find the greatest number that divides 388, 415, 550 leaving the same remainder in each case.

Find the greatest number that divides 125, 205, 365 leaving the same remainder in each case.