The sum of how many terms of the series 6 + 12 + 18 + 24 + ... is 1800 ? Options.
A) 19	B) 23	C) 13	D) 26	E) 24
This is an A.P. in which a = 6, d = 6 and Sn = 1800   Then,	n/2*	[2a + (n - 1)d] = 1800   n/2*	[2 x 6 + (n - 1) x 6] = 1800   2   3n (n + 1) = 1800   n(n + 1) = 600   n^2 + n - 600 = 0   n^2 + 25n - 24n - 600 = 0   n(n + 25) - 24(n + 25) = 0   (n + 25)(n - 24) = 0   n = 24   Number of terms = 24   Answer is 24.
<result>E</result>
The sum of how many terms of the series 6 + 12 + 18 + 24 + ... is 1800 ?