TEKS 4.4A · Grade 4

Adding and subtracting decimals

Column addition and subtraction with decimals to the hundredths, including borrowing across a zero.

The standard itself reads: “4.4A: add and subtract whole numbers and decimals to the hundredths place using the standard algorithm”

One of them, worked all the way through

1. Write 39.5 as 39.50 so both numbers go out to hundredths.
2. Line up the decimal POINTS, not the right-hand edges.
3. Subtract: 41.08 − 39.50 = 1.58 seconds.

This is one way, not the only way. The printable shows the same question worked more than one way, because children get there differently.

What usually goes wrong, and what helps

Each of these is a different misunderstanding rather than a slip, so each one needs something different. Find the one that sounds like your kid.

The student lines the numbers up on the right instead of on the decimal point

The decimal points go in a straight line down the page. Everything else follows from that one thing.

The student treats a missing decimal place as a column to skip rather than as a zero

Fill an empty place with a zero. 39.5 and 39.50 are the same number.

The student takes the smaller digit from the larger instead of regrouping

When the top digit is smaller, borrow. It is the same move as with whole numbers.

The student borrows across a zero without reducing the column the ten came from

A zero cannot lend anything until it has borrowed first. Work left until you reach a column that can give.

Try this at home

Have them write in the missing zero before they add: 12.4 becomes 12.40. Most decimal mistakes at this age are a column that had nothing in it rather than arithmetic gone wrong.

where these methods come from The strategies behind it: the Decimals chart.

What’s in the printable

Four questions on this skill, two to a page. The rest of the file is for the adult: an answer key, a worked solution for every question, and teacher pages on what each wrong answer means. 10 pages in all.