Question

Suppose you write 10 consecutive natural numbers on a board. When one of the numbers is erased, the sum of the remaining numbers is 2015. What number was erased?

*NOTE: If any troll/false responses are added, I won't hesitate to report.*

Answer 1

Note that 2016 = 9*224. Thus, 2016 can be represented as 220 + 221 + 222 + 223 + 224 + 225 + 226 + 227 + 228. Thus, the only 10 consecuetive numbers must have been close to those numbers. We just need to minue one from the sum of 220 to 228 to get 2015. Thus, by adding 219 and minusing 220, we get 2015. Hence, the 10 consecuetive natural numbers was 219 to 228, and 220 was erased.