Find the sum of the 1st 100 odd numbers.?

Question

the way i'm supposed to do it is in simpler form. so not counting 1 by 1 and adding it. something faster.

Answer 1

Well, first, the nth odd number is 2n-1.
So, the 100th odd numer is 2*100-1=199.
Now, notice if you add 100th and 1st odd number, 1+199, its same as adding 2nd and 99th =3+197=200.
So, this true with the rest of numbers.
So, the sum is (100/2)*200 = 10,000.

Answer 2

You'd take the first and last number of your sequence (1 and 199), then you'd find the sum and muliply by 50. The equation would be (pF+pL)x(totP/2)
F=first number
L=last number
totP=total numbers to be added