Question

The common difference of AP is -2 find it's sum if first term is 100 and last term is -10

Answer 1

Answer:

2520

Step-by-step explanation:

c=a+(n-1)d

c=-10

a=100

d=-2

-10=100+(n-1)(-2)

→-110=(n-1)(-2)

→-110/(-2)=n-1

→55=n-1

→n=56

sum = n/2(a+c)

→sum=56/2(100-10)

→sum=28*90

→sum=2520