Question

find the sum of natural no bw 250 and 1000 and exactly divisible by 3
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Answer 1

$\huge\mathcal\red{Answer}$

The first number after 250 divisible by 3 is 252.

and the number just before 1000 divisible by 3 is 999.

So there are 333–84+1 = 250 numbers between 250 and 1000 divisible by 3.

Their sum = (n/2)(a+l)

= (250/2)(252+999) = 156375.