Q2 of 85 Page 101

Determine if the following sequences represent an A.P., assuming that the pattern continues. If it is an A.P., find the nth term:

Natural numbers which are consecutive multiples of 5 in increasing order.

Formula Used.


dn = an + 1 – an


an = a + (n–1)d


The sequence of natural numbers which are consecutive multiples of 5


Is 5, 10, 15, 20 ……


In the above sequence,


a = 5;


d1 = a2–a1 = 10–5 = 5


d2 = a3–a2 = 15–10 = 5


d3 = a4–a3 = 20–15 = 5


As in A.P the difference between the 2 terms is always constant


The difference in sequence is same and comes to be 5.


The above sequence is A.P


The nth term of A.P is an = a + (n–1)d


an = a + (n–1)d = 5 + (n–1)5


= 5 + 5n–5


= 5n


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