Q30 of 89 Page 51

Find the sum of last ten terms of the AP 8, 10, 12, …, 126.

First term, a = 8

Common difference, d = 10 - 8 = 2

For finding, the sum of last ten terms, we write the given AP in reverse order.

i.e., 126, 124, 122, …., 12, 10, 8

and First term A = 126 and Common difference D = - 2

Sum of ten terms of new AP is

If sum of first 6 terms of an AP is 36 and that of the first 16 terms is 256, then find the sum of first 10 terms.

Find the sum of all the 11 terms of an AP whose middle most term is 30.

Find the sum of first seven numbers which are multiples of 2 as well as of 9.

How many terms of the AP - 15, - 13, - 11, … are needed to make the sum - 55?