SSC CHSL 15 Nov 2015 Shift 2 Paper

Question : 3 of 200

Marks: +1, -0

In the following series find 20th number
9, 5, 1, -3 -7, -11,........

Solution:

The given series is an arithmetic progression with first term a = 9 and common difference d = −4

n^{th}

term in an A.P. =

A_n = a + (n − 1)d

⇒

A_20 = 9 + (20 − 1) × (−4)

9 + (19)(−4)

9 − 76 = −67

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