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What is the sum of first 20 odd natural number?

  First of all we should know what is natural number- Natural Number- 1,2,3,4.....n Solve- Sum of first 20 odd natural number is- 1,3,5,7.....20 given here. We know that when we sum of these number then represent by 1+3+5+7....20 It is represented A.P series Here a= first term=1 d=common difference=2 n=20 Then we use A.P formula of sum. Sn=n/2[2a+(n-1)d] =20/ 2[2*1+(20-1)2 =10(2+38)         =10*40         =400. Ans
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