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FIND THE SUM OF FIRST 500 POSITIVE INTEGERS . WHAT ARE THE LAST 3 DIGIT OF THE SUM ?


The answer is 250.

Devesh Rai by Devesh Rai , 22, India

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3 solutions

Lauren Yeo
Dec 21, 2013

The sum of the first n natural numbers is n ( n + 1 ) 2 . \frac{n(n+1)}{2}. Substituting n with 500, we have the sum as 125250. Thus the last three digits are 250.

2 Helpful 0 Interesting 0 Brilliant 0 Confused

good.. carry on

sathiya narayanan - 7 years, 5 months ago
Victor Loh
Jan 16, 2014

500 ⋅ 501 2 = 125 250 \frac{500\cdot501}{2}=125\boxed{250} .

0 Helpful 0 Interesting 0 Brilliant 0 Confused
Sathiya Narayanan
Dec 21, 2013

n*(n+1)/2

0 Helpful 0 Interesting 0 Brilliant 0 Confused

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