" 13."25+28+31+...+100" Find the sum of "

Find the sum of -68 and 28

Find the sum of -68 and 28

Find the number of terms of the AP 18, 31/2, 13, ....., -99/2 and find the sum of all its terms.

Find the number of terms of the AP 18,(31)/(2),13,......,-(99)/(2) and find the sum of all its terms.

The sum of the squares of two positive numbers is 100 and difference of their squares is 28. Find the sum of the numbers:

Sum of first 10 terms of an AP is 100 andfirst 25 terms is 625. Find the numberof terms in it, whose sum is 441.

Find the mean of 25, 27, 19, 29, 21, 23, 25, 30, 28, 20 and prove that the sum of the deviation taken from the mean is zero.

Find : 31.1xx100