If the first term of an A.P. is 2 and common difference is 4, then the sum of its 40 terms is

Here a1= 2


D = common difference = 4


Sn = (2a + (n–1) d)


S40 = (2 x 2 + (39) 4)


= 20 (4 + 156)


= 3,200

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