The greatest common factor of two co-prime numbers will be

The HCF of two numbers is 21 and their LCM is 840. If one of the numbers is 49, then the other number is:

Find the LCM of the fractions $${2\over 5}$$, $${3\over 7}$$ and $${4\over 9}$$

Which of the following numbers is divisible by 11?

By what least number should 21600 be multiplied to make it a perfect square?

The sum of two and the product of 23 is 120. The sum of the areas will be:

The HCF of two numbers is 24. If sum of the numbers is 480, how many such pairs of numbers are possible?

The greatest four digit number which is exactly divisible by each one of the numbers 12, 18, 21 and 28.