Question

Every Number between 500 - 1000 that aren’t divisible by 7

Answer 1

Answer:

The numbers between 500 &

1000 divisible by 13:

507, 520,

here

t2t1 = t3 t2 = 13

This forms an A.P

a = 507, d = 13, tn = 988

We know that,

tn = a +(n - 1) d.. [formula]

988507 + (n - 1) 13 988 507 +13n - 13 =

988 494 + 13n 988 494 13n

494 = 13n 13n = 494

n = 494/13 n = 38

We know that,

Sn = (2a + (n − 1)d)

s38=3(2a +(38 - 1)d)

s38 = 19(2a +37d) -

s38 19(2 x 507 + 37 x 13)

s38 19(1014+ 481)

s38 = = 19 (1495)

988

s38 = 28405

Therefore,