Question on: JAMB Mathematics - 2009
The sum of the first n terms of the arithmetic progression 5, 11, 17, 23, 29, 35,... is
A
n(3n - 0.5)
B
n(3n + 2)
C
n(3n + 2.5)
D
n(3n + 5)
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Correct Option: B
Tn = (\frac{1}{2})n(2a + (n - 1)d)
= (\frac{1}{2})n(2 x 5 + (n - 1) 6
= (\frac{1}{2})n(10 + 6n - 6)
= n(\frac{1}{2})(6n + 4)
= n(3n + 2)
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