Multiplying decimals to hundredths
In 5th grade, children learn to multiply decimals to hundredths, like 4 × 0.75 and 0.2 × 0.3, using drawings and place value, and to explain where the decimal point lands in the written answer.
By Robert “Bobby” BarnettMath teacher, parent, and founder of Bobby’s Math Club
Try these with your child
These are real questions from our 5th grade practice. Tap the speaker to hear one read aloud, or the light bulb for a hint, and talk about the answer together.
Question 1 of 3
Which addition has the same value as 4 × 0.6?
- 6 + 6 + 6 + 6
- 0.6 + 0.6 + 0.6 + 0.6
- 4 + 0.6
Why this matters
Your child will reach for decimal multiplication whenever they need the cost of several things or a part of an amount. Three notebooks at $1.25 each, or half of a 1.5-liter bottle, are both decimal multiplication. It is the groundwork for percentages in 6th grade, where finding 25% of a price can mean multiplying by 0.25. You'll see it if you double a recipe or price 2.5 pounds of apples at the store.
If tenths and hundredths still feel shaky, it can help to go back to adding and subtracting decimals to hundredths first.
Where kids can get stuck
- Writing 0.2 × 0.3 as 0.6 instead of 0.06, not seeing that two tenths of three tenths is six hundredths.
- Placing the decimal point without checking the size, so 6 × 0.25 comes out as 15 or 0.15 instead of 1.5.
- Multiplying only the whole numbers, so 2.5 × 4 becomes 8 instead of 10, with the 5 tenths left out.
How you can help
- Use measuring cups while cooking. If one batch needs 0.75 cups of milk, ask how much four batches need. Your child can reason that four groups of 0.75 is 3 cups.
- Draw a 10 by 10 grid on paper. Shade 3 columns one way and 2 rows across them, then ask your child to count the squares shaded twice, 6 out of 100, and explain how that matches 0.2 × 0.3 = 0.06.
- Talk about parts of a trip in the car. If the drive is 3.6 miles and you are halfway, how far have you gone? Ask your child to say it as 0.5 × 3.6 and explain why 1.8 is less than 3.6.
Want a little more? Try Bobby's Math Club for free practice that adapts to your child.
Questions parents ask
Why is my child learning to multiply decimals with drawings?
Drawings show what the product means. When your child shades 3 tenths four times and sees 12 tenths, the answer 1.2 is something they understand, not a rule about moving a point. On a hundredths grid, 0.2 × 0.3 is a small rectangle of 6 squares out of 100, which is why it is 0.06. Later, counting decimal places will feel like a shortcut they can trust.
Why did my child get a smaller answer when multiplying decimals?
Multiplying by a number less than 1 gives a smaller result. For example, 0.5 × 8 = 4, because half of 8 is 4. Many children are surprised, since multiplying by a whole number bigger than 1 always made things bigger. Talking about "half of" or "three tenths of" an amount helps your child see why the answer shrinks.
My child adds decimals well, so why is multiplying harder?
Adding keeps the places lined up, so tenths go with tenths. Multiplying mixes them: tenths times tenths makes hundredths, which is a new idea. It helps to start with a whole number times a decimal, such as 3 × 0.7, which is three groups of 7 tenths, or 2.1. Once that feels steady, move on to a decimal times a decimal.
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Written by Robert “Bobby” Barnett
Bobby is an award-winning math teacher, the author of Meet Every Learner’s Needs, and the father of two elementary-school math learners. He uses Bobby’s Math Club with his own kids a few times every week. Learn more or contact Bobby.
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Join the clubNote for teachers: This skill is covered by Common Core math standard 5.NBT.B.7: “Add, subtract, multiply, and divide decimals to hundredths, using concrete models or drawings and strategies based on place value, properties of operations, and/or the relationship between addition and subtraction; relate the strategy to a written method and explain the reasoning used.” Learn how Bobby's Math Club can help your students grow. (Common Core 5.NBT.7)