Find the mean of all possible factors of 20.

Find the number of all possible matrices of order 2xx2 with entries 0,1 or 2.

Find the sum of all possible products of the first n natural numbers taken two by two.

Find the mean of all factors of 10.

A sample of 3 bulbs is tested. A bulb is labelled ‘G’ if it is good and ‘D’ if it is defective. Find the number of all the possible outcomes.

Find the number of proper factors of the number 38808. Also, find sum of all these divisors.

The number k is such that tan { arc tan (2) + arc tan (20 k) } = k . The sum of all possible values of k is

The mean of first 8 observations is 18 and last 8 observations is 20. if the mean of all 15 observations is 19, find the 8th observations.

The mean of 20 numbers is 18, if 3 is added to each of the first ten numbers, find the mean of the new set of 20 numbers.