Question

first term and common difference of an a.p. are 3 and 6 respectively find s15​

Answer 1

Answer:

A1=3 D=6

we know,

tn=A+(n-1)×d

19=3+(n-1)×6

19=3+6n-6

19=-3+6n

19+3=6n

n=22/6

therfore S15 is 22/6

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