Question

if n=11,a=40,d=-4 find sn​

Answer 1

Answer:

220

Step-by-step explanation:

Given:- n=11, a=40, d=-4

Sn=n/2[2a+(n-1)d]

S11=11/2[2*40+10*(-4)]

=11/2[80-40]

=11/2[40]

=11*20

=220

Answer 2

GIVEN :

First term of AP = a = 40

Common Difference = d = -4

number of terms = 11

nth term = an = a + (n - 1)d

an = 40 + (11 - 1)-4

= 40 + (10)-4

= 40 - 40

an = 0

Sum of terms = Sn = ?

We know that,

In an AP sum of terms, Sn = n/2 [ a + an]

Sn = 11/2 [ 40 + 0]

= 11/2 [ 40 ]

= 11[20]

Sn = 220

Therefore, the sum of the AP is 220.