SSC MTS Model Paper 1

Question : 39 of 150

Marks: +1, -0

If the 4th term of an arithmetic progression is 16 and the 12th term is 80, then find the first term.

– 8
– 7
+ 7
+ 8

Solution:

_{4}

= a + (4 – 1) × d
16 = a + 3d ⇒ a = 16 – 3d...(1)
Also, 80 = a + 11d...(2)
After putting the value of a from equation (1) in equation (2)
16 – 3d + 11d = 80
⇒ 8d = 80 – 16 = 64
⇒ d = 8
∴ a = 16 – 24 = – 8

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