SSC CGL Model Paper 4

Question : 64 of 100

Marks: +1, -0

If the 3rd and the 5th term of an arithmetic progression are 13 and 21, what is the 13th term?

Solution:

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

A _3 = a + (3 - 1 ) d

⇒

13 = a + 2d

...(i)

A_ 5 = a + (5 - 1) d

⇒

21 = a + 4d

...(ii)
On solving Eqs. (i) and (ii),
a = 5 and d = 4
⇒

A_13 = a + (13 - 1 ) d

⇒

A_13 = 5 + 1 2× 4

A_13 = 5 + 48 = 53

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