Find the difference between any two consecutive terms consecutive terms in the sequence.

How to subtract the first term of the sequence by the second one.

10th Maths EXERCISE 5.3, Page No:112, Questions No:1 Part (iv).

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# Find the sum of the following APs: 1/15, 1/12, 1/10, …, to 11 terms.

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A.P. 1/15, 1/12, 1/10, …

Here, a = 1/15 and d = 1/12 – (1/15) = 1/60.

The sum of n terms of an AP is Given by

Sn = n/2[2a + (n -1)d]

The sum of n terms of an AP is given by

S_n = n/2[2a + (n – 1)d

⇒ S₁₁ = 11/2[2(1/15) + (11 – 1) (1/60)]

⇒ S₁₁ = 11/2[2/15+ 1/6] = 11/2[9/30] = 33/20.