Question

4. The first term of an A.P is 2 and the nth term is 41. What is the value of n, if
Sn=860?
(A) 30
(B) 31
(C) 41
(D) 40​

Answer 1

The answer is d part that is 40 . Please mark me the brainliest thank u

Answer 2

Answer:

given : a = 2 , nth term = 41 , sum of n terms = 860

nth term = a + ( n - 1 ) d

41 = 2 + ( n - 1 ) d

39 = ( n - 1 ) d

d = 39/ ( n - 1 )

now,

sum of n terms= n/2[ 2a+(n-1)d]

860 = n/2[2×2 + (n-1) × 39/(n-1)]

1720 = n [ 4 + 39 ]

1720/43 = n

n = 40