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Sum of first terms of an A.P. is 9 less ...

Sum of first terms of an `A.P.` is 9 less than the sum of next 3 terms of the same `A.P.` and second term is 2 then `4^(th)` term of that `A.P.` is :

A

`12`

B

`4`

C

`15`

D

`18`

Text Solution

Verified by Experts

The correct Answer is:
B
Sum of first three………….
`S_(3)= (S_(8)-S_(3))-9`
`2.S_(3)= S_(8)-9`
`2.(3)/(2)(2a+2d)= (6)/(2)(2a+5d)-9`
`6a+6d=6a+15d-9`
`9d=9 implies d = 1`
also `T_(2)=a+b2implies a =1`
`:. T_(4)=a+3d=4`
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