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 upto 12 terms.
CBSE DHANPAT RAI PUBLICATIONS
Understanding CBSE Mathematics
Class :- 10th
Question no 1(iv)
Given A.P. has first term(a) = 41,
Common difference(d) = 36 – 41 = -5
and number of terms(n) = 12
So, Sum of A.P. = S12 = n[2a + (n – 1)d] / 2
= 12[2(41) + (12 – 1)(-5)]/2
= 12[82 – 55] = 162
Hence, the sum of the first 12 terms of A.P. is 162.