Question

Find the 11th partial sum of (picture in comments)

Answer 1

A -220
B 400
C 550
D -700

Answer 2

@D3xt3R

Answer 3

@zaibali.qasmi

Answer 4

@ganeshie8 plz help this girl ..!!

Answer 5

sorrrey..

Answer 6

@ceol1998

Answer 7

remember the sum of n terms formula for arithmetic series ?

Answer 8

An=A1+(n-1)d?

Answer 9

thats nth term formula,
lookup `sum of n terms` formula

Answer 10

\[\large S_n = \dfrac{n}{2}\left[2a+(n-1)d\right]\]

Answer 11

\(n=11\)
\(a = -7(1) + 22 = 15\)
\(d = -7\)

plug them and simplify

Answer 12

thank you :)