1.

If the 3rd and the 5th term of an arithmetic progression are 13 and 21, what is the 13th term?1). 532). 493). 574). 61

Answer»

Let the first term of AP be a and common difference be d

From the problem’s statement

⇒ 3rd term = a + (3 - 1) d = a + 2d = 13----(i)

⇒ 5th term = a + (5 - 1) d = a + 4D = 21----(ii)

Now (ii) - (i)

⇒ 2d = 8

⇒ d = 4, PUT this in (i)

⇒ a = 13 - 8 = 5

Now the 13th term can be given as a + 12d

⇒ 13th term = 5 + 12 × 4 = 53

∴ the 15th term of AP is 53


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