SOLUTION: What is the sum of the first eleven terms of the arithmetic sequence 3, 5 1/2 , 8, ...... ? a 28 b 143 1/2 c 154 d 170 1/2 e 175

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Question 364073: What is the sum of the first eleven terms of the arithmetic sequence
3, 5 1/2 , 8, ...... ?
a 28 b 143 1/2 c 154 d 170 1/2 e 175

Answer by vasumathi(46) About Me  (Show Source):
You can put this solution on YOUR website!
Solution : The first term = 3
so a = 3
and the difference between the second and the first is
5 1/2 - 3 = 2 1/2
so d = 2 1/2 = 5/2
the number of terms = 11
so n = 11
then the sum of first eleven numbers of this series is as follows....
S = (n/2)(2a + (n-1)d)
S = 11/2 (2*3 + (11-1)*(5/2))
S = 5.5 ( 6 +10 * 5/2)
S = 5.5(6 +25)
S = 5.5 * 31
S = 170.5 = 170 1/2
So the choice "d" is correct