Math, asked by shreejanibadhiya, 8 months ago

If 3rd and 10th terms of an A.P. is 9 and 21. Then find the sum of first 12 terms ​

Answers

Answered by mitraayushi2020
4

Answer:

180

Step-by-step explanation:

A.T.P.,

a+2d=9

a+9d=21

Solving simultaneously,

a+9d=21

a+2d=9

Subracting, we get 7d=12

d=12/7

a=21-9*12/7

 =21-108/7

=(147-108)/7

=39/7

sum of 12 terms=6(78/7+132/7)

=6*30

=180

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