Question

8. Find the sum of all multiples of 9 lying between 700 and 900.

Answer 1

Answer:

Hope it helps

Step-by-step explanation:

Hope my answer is correct

702+711+720------------------900=18423

Please mark me as a brainliest

Answer 2

Answer:

17523

Step-by-step explanation:

Multiples of 9 lying between 700 and 900 are,

702, 711, 720,.......,891 [we must not take 900 as in the question, it is given between 700 and 900, that means 700 and 900 are not included, but if it gives from 700 to 900, then both the numbers are included.]

l[last term] = a[first term] + (n[number of terms] - 1)d[common difference]

l = a + (n - 1)d

891 = 702 + (n - 1)9

189 = (n - 1)9

21 = n - 1

n = 22

$S_{n}$  = n/2(a + l)

$S_{n}$  = 22/2(702 + 891)

$S_{n}$  = 11(1593)

$S_{n}$  = 17523

The required sum is 17523.

Hope this helps you!!