When you work with decimal math, especially when adding and subtracting, there are some common mistakes students make. Here are a few things to watch out for to get the right answers.

1. Misaligning Decimal Points

One big mistake is not lining up the decimal points correctly.

When you add or subtract decimals, always make sure the decimal points are in a straight line.

For example:

  12.34
+  3.7

It’s better to write it like this:

  12.34
+  3.70

Now you can see that the numbers line up. This helps you avoid making mistakes in your calculations.

2. Ignoring Place Values

Another mistake is not paying attention to the place values of the digits.

When you add $0.5 + 0.25$, think of $0.5$ as $0.50$.

This helps you line up the numbers better:

$$\begin{array}{r} 0.50 \\ + 0.25 \\ \hline 0.75 \\ \end{array}$$

3. Not Carrying Over

Sometimes, when the total is more than $10$ in a decimal problem, students forget to carry over.

For example, when you add $9.7 + 2.6$, the answer should be $12.3$, not just $11.3$.

Conclusion

If you pay attention to these common mistakes, you will have more accurate and confident answers when adding and subtracting decimals.

Happy calculating!