Adding and Subtracting Decimals to Hundredths

When working with decimal numbers, adding and subtracting is just like working with whole numbers. The most important rule to remember is to line up the decimal points.

Steps for Adding and Subtracting Decimals

1. Line up the decimal points vertically. This ensures you are adding or subtracting tenths with tenths, and hundredths with hundredths.
2. Fill in empty spots with zeros so both numbers have the same number of decimal places.
3. Add or subtract exactly as you would with whole numbers (remember to regroup or borrow if needed).
4. Bring the decimal point straight down into your final answer.

Example 1: Addition

Let's solve: $3.45 + 2.7 = ?$

First, line up the decimals and add a placeholder zero to $2.7$ so it becomes $2.70$.

$$\begin{array}{r} 3.45 \\ + 2.70 \\ \hline 6.15 \end{array}$$

The answer is $6.15$.

Example 2: Subtraction

Let's solve: $5.03 - 1.28 = ?$

Line up the decimals. Since both already go to the hundredths place, we don't need extra zeros. Subtract just like whole numbers, borrowing from the $5$ to give to the $0$, and then the $3$.

$$\begin{array}{r} 5.03 \\ - 1.28 \\ \hline 3.75 \end{array}$$

The answer is $3.75$.

Real-World Example

Problem: A ribbon is $3.5$ m long. After cutting $1.75$ m, how much remains?

This is a subtraction problem: $3.5 - 1.75$. Line up the decimal points and add a zero to $3.5$ so it becomes $3.50$.

$$\begin{array}{r} 3.50 \\ - 1.75 \\ \hline 1.75 \end{array}$$

There is $1.75$ m of ribbon remaining.