Find the sum of the first 20 terms of the series 8, 12, 1...
Find the sum of the first 20 terms of the series 8, 12, 16, ....., 96
1400
1040
960
920
Correct answer is D
8, 12, 16, .....96
a = 8, d = 4, l = 96, n = 20
\(S_{20} = \frac{n}{2}(2a + (n-1)d\)
\(S_{20} = \frac{20}{2}((2\times 8) + (20-1)\times 4)\)
\(S_{20} = 10(16 + (19\times 4)) = 10 \times 92\)
=920
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