Question

for an Ap T1 =2 Tn =41 Sn = 860 then find n​

Answer 1

To find:-

n

Solution:-

Sn =860

T1 = 2

Tn = 41 , Tn = [a +( n-1 )d ]

n =?

SN = n/2 (2a + {n-1}d ) = 860

n/2( 2× 2+ (n-1)d ) = 860

n/2 (tn+t1) = 860

n/2 (41 +2) = 860

n/2 (43) = 860

n = (860 ×2 )/43

n = 40

Hope it helps you!!