Rounding

Remember, when we round numbers to the nearest 10 without using the number line, we look at the digit in one's place.  If the number has 4 or less ones, we round the number down to the nearest 10.  If the number has 5 or more ones, we round the number up to the nearest 10.

We want to round numbers to nearest 100.  The number 217 is closer to 200 than 300.  The number 217 rounded to the nearest 100 is 200. 

The number 1,150 is the same distance from 1,100 and 1,200.  Any number that ends with 50 (has a 5 in ten's place) is rounded up to the nearest 100.  The number 1,150 rounded to the nearest 100 is 1,200.

When we round numbers to the nearest 100, we follow the same simple rules, only we look at the digit in tens' place.

1. If the number has a 4 or less tens, we round the number down to the nearest 100.  The number 217 has a 1 in ten, so 217 rounded down to 200.

2. If the number has 5 or more tens, we round the number up to the nearest 100.  The number 782 has 8 tens, so 782 is rounded up to 800.  The number 1,150 has 5 tens, so 1,150 is rounded up to 1,200.