Skill: Solve decimal measurement problems

A decimal measurement tells how much of a unit you have. The first digit after the decimal shows tenths, and the second shows hundredths.

When solving a measurement problem:

1. Make sure both measurements use the same unit.
2. Line up the decimal points.
3. Add or subtract by place value.
4. Label the answer with the correct unit.
5. Estimate to check that the answer makes sense.

Example: A ribbon is $2.75\text{ m}$ long. Mia uses $1.4\text{ m}$. How much ribbon is left?

Both measurements are in meters. Write $1.4$ as $1.40$ so the place values line up:

$$\begin{array}{r} 2.75\\ - 1.40\\ \hline 1.35 \end{array}$$

Subtract by place value:

• $5$ hundredths minus $0$ hundredths is $5$ hundredths.
• $7$ tenths minus $4$ tenths is $3$ tenths.
• $2$ ones minus $1$ one is $1$ one.

So, the amount of ribbon left is

$$\boxed{1.35\text{ m}}$$

An estimate is $2.8-1.4\approx1.4$, so $1.35\text{ m}$ is a reasonable answer.