Question

The 10th term of an AP is 52 and 16th term is 82 find
(iii) sum of first 20 terms of an AP
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Answer 1

Step-by-step explanation:

Let a be the first term and d be the common difference of the given A.P. 

Let the A.P. be a1,a2,a3,....,an,...

It is given that

a10=52 and, a16=82

⟹a+(10−1)d=52 and, a+(16−1)D=82

⟹a+9d=52                       ...(i)

and a+15d=82                     ...(ii)

Subtracting equation (ii) form equation (i), we get

−6d=−30⟹d=7

Putting d=5 in equation (i), we get

a+45=52⟹a=7

∴a32=a+(32−1)d=7+31×5162

and, an=a+(n−1)d=7(n−1)×=5n+2

Hence, a32=162 and an=5n+2

Answer 2

Answer:

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