Which letter-cluster will replace the question mark (?)

The product of two positive integers is 1620. If their HCF is 9 and their sum is 81, then find the difference between the numbers.

Determine the highest common factor (HCF) of the numbers 75, 125, and 300.

Let N be the greatest number that will divide 85, 112, 139 leaving the same remainder in each case. Then sum of the digits in N is:

Calculate the Least Common Multiple (LCM) of the two highest prime numbers under 10.

A car moves 144 km in 4 hours. The bike goes 1.5 m/s slower than the car. What distance (in metres) does the bike cover in 6 minutes 20 seconds?

Let N be the greatest number that will divide 92, 114, 136 leaving the same remainder in each case. Then sum of the digits in N is:

The H.C.F. of two numbers is 22 and the other two factors of their L.C.M. are 9 and 11. The larger of the two numbers is:

Two numbers are in the ratio 3:7. The product of their H.C.F. and L.C.M. is 2541. The sum of the numbers is:

Find the largest number of the five digit which is exactly divisible by 48, 72 and 108.