Find the sum of all odd numbers upto 100.
Choose the correct answer.
A) 2200 B) 2900 C) 2700 D) 2500 E) 2800
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.   Therefore, Required sum = n/2 (first term + last term)   = 50/2 (1 + 99) = 2500.   Answer is 2500.
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Find the sum of all odd numbers upto 100.