Question

What is the sum of the geometric series 20 + 21 + 22 + 23 + 24 + … + 29?

Answer 1

When you add 20 and 29, you get 49. When you add 21 and 28, you get 49. You will realize that there's 5 pairs that result in a sum of 49. 5*49=245.

Answer 2

1023

Explanation:

2^0+2^1+2^2+2^3+2^4+2^5+2^6+2^7+2^8+2^9

1+2+8+16+32+64+128+256+512=1023