Math, asked by pmanoj9271, 11 months ago

What is the sum of the first
11 terms of an arithmetic
progression if the 3rd term is -1
and the 8th term is 19?
(A) 204 (B) 121 (C) 225 (D) 104
1.B 2.A 3.C 4.D

Answers

Answered by sinhashubham114

0

Answer:

S11=

A3= a+2d

-1= a+2d

A8= a+7d

19= a+7d

19=-2d- 1 +7d

20= 5d

d=4

a=-9

S11= 11/2 [2*-9 + 10*4]

= 11/2 [-18+40]

= 11/2 *32

= 16*11

=176

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