Question

11. Find the sum of all 3-digit numbers which are
divisible by 13.​

Answer 1

Answer:

This is a kind of question related to the A.P.(Arithmetic Progression)

Here common difference , d=13

first term,a=smallest 3 digit number divisible by 13=104

nth term,tn = largest 3 digit number divisible by 13=988

we know =

tn=a+(n-1)*d            // n is the number of terms

988= 104+(n-1)*13

n-1=68

n=69 terms.

Sum = n/2(a+tn)

       =69/2(104+988)

       37,674..

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