Question

An AP consists of 50 terms of which 3rd term is 12 and the last term is 106 find the sum of 25 terms.​

Answer 1

Answer:

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An AP consists of 50 terms of which 3rd term is 12 and the last term is 106 find the sum of 25 terms.

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a+2d=12

a+49d=106

⇒47d=94

⇒d=2

a+4=12

⇒a=8

29 term:-

a+ 28d = 8+56= 64

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Answer 2

Explanation:

a3 = a + (3 — 1) d

12 = a + 2d

12 – 2d = a... (1)

a50 106

050 = a + (50 – 1) d

106 = a + 49d

106 – 49d = a.... (2)

12 - 2d = 106 – 49d

-2d + 49d = 106 – 12

d=2