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Question

In an A.P., let Tn denotes the nth term and Sn denotes the sum of first n terms. If T7=19 and T9=17, then the value of S63 is

A
32
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B
49
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C
56
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D
63
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Solution

The correct option is A 32
Let a and d be the first term and common difference of A.P. respectively.
Then, T7=a+6d=19 (1)
and T9=a+8d=17 (2)

Solving (1) and (2), we get
a=163,d=163S63=632[2a+(631)d]=632[2×163+62×163]=32

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