This is an arithmetic progression based question from Chapter name- Arithmetic Progression
Chapter number- 9
Exercise – 9.6
In this question we have been given the arithmetic progression. Also we have to find the sum of it.
CBSE DHANPAT RAI PUBLICATIONS
Understanding CBSE Mathematics
Class :- 10th
Question no 13(vii)
Given series is an A.P. with first term(a) = 25,
Common difference(d) = 28 − 25 = 3 and nth term(an) = 100.
We know nth term of an A.P. is given by, an = a + (n − 1)d.
=> 100 = 25 + (n − 1)(3)
=> 100 = 25 + 3n − 3
=> n = 88/3
=> n = 26
Also we know sum of n terms of an A.P. is given by Sn = n[a + an]/2.
S26 = 26[25 + 100]/2
= 13(125)
= 1625
Hence, the sum of terms of the given series is 1625.