common difference of an arithmetic progression is 3 and find a20 - a15

Asked by Kapil | 20th Oct, 2017, 09:59: AM

Expert Answer:

 
We know that the common difference is given as '3'.
Let 'd' be the common difference, 'a' be the first term, so the nth term is written as straight a subscript straight n equals straight a plus left parenthesis straight n minus 1 right parenthesis straight d
 
We will have to find straight a subscript 20 minus space straight a subscript 15
Applying the formula, the above expression becomes,
(a+19d) - (a+14d)
= a + 19d - a - 14d
= 5d
This finally becomes
5 x 3
=15

Answered by  | 14th Dec, 2017, 05:13: PM