Question

find the common difference of an AP whose first term is 4 ,the last term is 49 and the sum of all it's term is 265

Answer 1

a=4

an=a+(n-1)d

49=4+(n-1)d

(n-1)d=45...(i)

sn=n/2[2a+(n-1)d]

265=n/2[8+45] [from (i)]

530=53n

n=10...(ii)

substituting (ii) in (i),

9d=45

d=5

Hence common difference is 5.

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