The greatest number when divide 147,185 and 251 leaving the remainders 3,5 and 11.Means the greatest number is not exactly dividing the given numbers. If we subtract the remainders from the respective numbers, then they are exactly divisible by the greatest numbers. The required greatest number = HCF of (147 - 3),(185-5) and ( 251-11) =HCF of 144,180 and 240 =12