Find the sum of all odd numbers upto 100.  Choices:  A) 200  B) 1000  C) 2500  D) 3140  E) 3200
Sol. The given numbers are 1, 3, 5, 7, ..., 99.   This is an A.P. with a = 1 and d = 2.   Let it contain n terms. Then,   1 + (n - 1) x 2 = 99 or n = 50.   Required sum = (n/2) (first term + last term)   = 50(1 + 99)/2 = 2500.   ANSWER 2500 2500
<result>C</result>
Find the sum of all odd numbers upto 100.