what is the sum of the first 20 odd natural numbers

• sum of first n odd natural nuber is = n^2
  so sum of the first 20 odd natural numbers=(20)^2=400
  ans 400
• 10 years agoHelpfull: Yes(27) No(6)
• Sum of first two odd numbers is 4, which is 2 square
  Sum of first three odd numbers is 9, which is 3 square
  So, sum of first 20 odd numbers is 20 square, which is 400
  
  Answer is 400
• 10 years agoHelpfull: Yes(16) No(1)
• SERIES IS IN AP.
  1 3 5 7 . . . . . . .
  20TH TERM(L)=A+(N-1)*D=1+(20-1)*2=39
  SUM OF 20 TERM=20/2(A+L)=10*(1+39)=400
• 10 years agoHelpfull: Yes(12) No(0)
• 4*(1+3+5+7+9) + (10*5) + (20*5) + (30*5) = 400
• 10 years agoHelpfull: Yes(4) No(1)
• firt odd natural number is = 1
  second odd natural no is = 2+1=3
  third odd natural no is = 3+2=5
  four odd natural no is =4+3=7
  fifth odd natural no is = 5+4=9
  .
  .
  .
  20 odd natural no is = 20+19=39
  
  here firt term is = 1
  comman diffrence is =2
  no to terms= 20;
  with the help of arithmatic sum
  sum of n no=2*a+(n-1)*d
  or
  a+l;
  where l =last term
  putting the value
  sum of 20 natural no is=1+39=40
  or
  2*1+(20-1)2
  2+19*2
  2+38=40 answer
• 10 years agoHelpfull: Yes(3) No(21)
• 1,3,5,7......19=10 numbers
  n(1st num+last num)/2=10(1+19)/2=5*20=100
• 10 years agoHelpfull: Yes(2) No(1)
• total no n=20
  sum=n/2 [1st turm + (n-1)d] d=difference
  =20/2 [1+(20-1)2]
  =400
• 9 years agoHelpfull: Yes(1) No(0)
• No need to do long method...simply in 1 line ans can be found.....
  
  here n=20, so sum of odd no=(n^2)....so ans is 400.
• 9 years agoHelpfull: Yes(1) No(0)
• here no. of terms =20
  and use sum of A.P i.e
  sum=n/2[2a+(n-1)*d]
  here a=1 and d=2
  so 400 will be the answer
• 8 years agoHelpfull: Yes(0) No(0)