In the laws of mathematics, especially in rounding off digits, you should take note of the digit following that number no matter how long or short a number is. If the number is preceded by numbers between 0-4, the number does not change. However if its is preceded by numbers between 5-9, add one to the number. In this problem, you are required to round off each number to the nearest ten million before adding them. So 0.9998 is equal to 1