Question

Find the sum of the numbers between 60 and 80 which are divisible by 9.

Answer 1

Answer:Its 135

Step-by-step explanation:

Here, a = 63

d = 9 ... And an = 72

an= a + (n -1)d

72= 63 + ( n-1) 9

n= 2

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

=1(126 + 9)

=135

Answer 2

63 and 72 are the only numbers between 60 and 80 which are divisible by 9.

Step-by-step explanation:

63/9 = 7

72/9 = 8