What is the sum of all odd numbers from 1 to 201?
1+2+3+4+5..+201 S201 = 201 (1+201)/2=101201 Sum of even 2+4+6+8+200 =2 [1+2+3+4+..+100] S( even)= 2 [ 100 (100+1)/2 =100101 S(odd)= S201 - S(even) =(101201)-(100101) .=101 (201-100) = 101101=10201 Or We have to find out 1+3+5+7+..+201 Number of terms =101 First term = 1 Last term = 201 In any AP series sum of series is = Sn =n [a+l]/2 Where n= number of terms a =first term and .. l= last term Sum of odd = 101 (1+201)/2= 101101 =10201