1.

Find the sum of all the 3 digit natural number which are divisible by 13.

Answer»

Heya mate, Here is UR answer

a(first TERM) = 104

d(common difference)=13 (divisiblity by 13)

an(LAST term) =988

a+(n-1)d =988

104+ (n-1)13=988

(n-1)13=988-104

(n-1)13=884

n-1=884/13

n-1= 68

n=68+1

n=69.

Sn = n/2 (a+an)

sn = \frac{69}{2} \times (104 + 998)


sn = \frac{69}{2} \times 1102

sn = 69 \times 551



sn = 38019



So, sum of 3 digits number divisible by 13 =38019 .

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WARM REGARDS

@Laughterqueen

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