Question

the sum of all integers between 200 and 700 which are divisible by 9 is​

Answer 1

Answer:

Since the AP sequence will

207 , 216 , 225 ............, 693

a = 207

d = 9

l = 693

Formula for number of terms

====>

l = a + (n-1) d

693 = 207 + ( n-1)9

468 = 9n -9

495 = 9n

495/9 = n

n = 55

Now formula for sum of n terms

=====>

Sn = n/2( a+l)

Sn. = 55/2(207+693)

Sn = 55× 900/2

Sn = 55 × 450

Sn = 24750

Hope it helps