Calculate the sum of first 39 natural numbers.	Pick
A) 780  B) 891  C) 812  D) 847  E) 890
Solution   We know that(1+2+3+.....+39)	= n(n+1)/2   Therefore (1+2+3+....+39)	=(39×40 / 2)   = 780.   780nswer 780
<result>A</result>
Calculate the sum of first 39 natural numbers.