Q. 115.0( 4 Votes )

If an denotes the nth term of the AP 2, 7, 12, 17, ..., find the value of (a30 – a20).

Answer :

Here, First term = a = 2

Common difference = d = 7 - 2 = 5


To find: a30 – a20


So, nth term is given by:


an = a + (n - 1)d


30th term is:


a30 = 2 + (30 - 1) × 5


= 2 + 145


= 147


Now, 20th term is:


a20 = 2 + (20 - 1) × 5


= 2 + 95


= 97


Now, (a30 – a20) = 147 - 97


= 50


(a30 – a20) = 50


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