SSC CGL Model Paper 10

Question : 64 of 100

Marks: +1, -0

The 5th and 9th term of an arithmetic progression are 7 and 13 respectively. What is the 15th term?

Solution:

T_n = a + ( n - 1) d

⇒

7 = a + ( 5 - 1 ) × d

∴ 7 = a + 4d ...(i)
⇒ 13 = a + ( 9 - 1 ) d
∴ 13 = a + 8d ...(ii)
On solving Eqs. (i) and (ii),

a - 1 \and d =3/2

Hence,

T_15 = 1 + (15 -1)×3/2

=1+14×3/2

= 1 + 21=22

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