Read it through once

I have before me statistics covering a period of six consecutive years. By these, I know that in India the tiger kills something over 800 persons every year, and that the government responds by killing about double as many tigers every year. In four of the six years referred to, the tiger got 800 odd; in one of the remaining two years he got only 700, but in the other remaining year he made his average good by scoring 917. He is always sure of his average. Anyone who bets that the tiger will kill 2,400 people in India in any three consecutive years has invested his money in a certainty; anyone who bets that he will kill 2,600 in any three consecutive years, is absolutely sure to lose.