To determine the correct answer for when a number should be rounded up, we need to understand the basic rule of rounding numbers.
When rounding a number:
1. Identify the digit you are rounding to.
2. Look at the digit immediately to the right of the digit you are rounding to (this is the key digit for the rounding decision).
3. Apply the following rules:
- If the key digit (the digit to the right) is between 0 and 4, the digit you are rounding to stays the same.
- If the key digit is between 5 and 9, the digit you are rounding to is increased by 1 (rounded up).
Based on this rule, we see that rounding up occurs when the digit immediately after the one you are rounding to falls between 5 and 9.
Thus, the best answer is:
c. the number after it is between 5 and 9
So, the correct choice is:
O C
