Skill: Check precision and rounding

Precision tells how finely a measurement is given. For example, $3.476$ has more precision than $3.5$ because it gives information to the thousandths place instead of only the tenths place.

To round a number:

1. Find the place value you are rounding to.
2. Look at the digit immediately to its right.
3. If that digit is $5$ or more, increase the rounding digit by $1$. If it is less than $5$, leave the rounding digit unchanged.
4. Remove the digits to the right.

Example: A trail is $3.476$ kilometers long. Report its length to the nearest tenth.

• The nearest tenth is the tenths place:

$$3.476$$

• The tenths digit is $4$.
• The digit to its right is $7$. Since $7$ is at least $5$, increase the $4$ to $5$.
• Remove the remaining digits.

Therefore,

$$3.476 \approx 3.5\text{ km}$$

The answer is appropriate if the distance only needs to be given to the nearest tenth of a kilometer. It is less precise than $3.476$ km, but it still shows the requested level of accuracy.

You can also check using a number line. The number $3.476$ is between $3.4$ and $3.5$, and it is closer to $3.5$, so rounding to the nearest tenth gives $3.5$.