This question is from Ncert Book class 10th Ch. no.5 Ex. 5.2 Q. 2 (ii) . In the following question you have to find the right option & justify your answer by giving the solution. This question uses fundamental idea of A.P.
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Choose the correct choice in the following and justify:- (ii)11th term of the A.P. -3, -1/2, ,2 …. is (A) 28 (B) 22 (C) – 38
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Solution:
A.P. = -3, -1/2, ,2 …
So, we can find,
1st value, a = – 3
C.D , d = a2 − a1 = (-1/2) -(-3)
=(-1/2) + 3 = 5/2
For an A.P we know:_
an = a+(n−1)d
Putting down the above values:-
a11 = 3 + (11 – 1)(5/2)
a11 = 3 + (10)(5/2)
a11 = -3 + 25
a11 = 22
So, the answer of the above series is B.