Question

Find the sum of all numbers between 10 to 40. (with procedure)
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Answer 1

Answer:

(sum of natural numbers from 1 to 40) - (sum of natural numbers from 1 to 10).

Sum of natural numbers from 1 to n can be denoted by (n).(n+1)/2.

So sum of natural numbers from 1 to 40 would be (40)x(40+1)/2 = 40x41/2 = 820.

Similarly sum of natural numbers from 1 to 10 be 10x(10+1)/2 = 10x11/2 = 55.

And hence, the answer to your question comes down to 820 - 55, which gives us the answer 765

Answer 2

Answer:

11+12+13+14+15+16+17+18+19+20+21+22+23+24+25+26+27+28+29+30+31+32+33+34+35+36+37+38+39+40= 765.