Question

plz guys need answer immediately..need answer for the 9 th one....​

Answer 1

Answer:

sum=120.

Step-by-step explanation:

To find the sum firstly we should find the n (number of terms in the given A.P) using this formula:   l=a+(n-1)d.

given a=5(first term=5) and d=11-5=6 (common difference=2nd term - first term)

l=a+(n-1)d.

35=5+(n-1)6

35=5+6 n-6

35= -1+6 n

6 n=36

n=6.(number of terms in given AP is 6)

Then after finding n we should use this formula to find (the formula which includes the 'l' because in the given question last term(l) is known:

s=n/2(a+l)

s=6/2(5+35)

s=3(40)

s=120.

Therefore, the sum of the given AP is 120.

Hope this helps you:) All  the best!!