Math Expressions Grade 5, Unit 4: Multiplication with Whole Numbers and Decimals
In this unit, your child multiplies multi-digit whole numbers with the usual written method and then multiplies decimals. Patterns with 10, 100, and 1,000 show why digits shift places, which helps them place the decimal point in products like 0.3 × 0.4. It follows the fraction multiplication unit and leads into dividing whole numbers and decimals.
By Robert “Bobby” BarnettMath teacher, parent, and founder of Bobby’s Math Club
What is my child learning in Unit 4?
- Seeing how multiplying by 10, 100, or 1,000 moves each digit to a larger place, and writing powers of 10 with exponents. Learn more: Multiplying and dividing by 10, 100, and 1,000
- Multiplying whole numbers, like 213 × 32, with the usual written method and checking with an estimate. Learn more: Multiplying big numbers, like 213 × 32
- Multiplying decimals by whole numbers and by other decimals, like 0.3 × 0.4, and placing the decimal point using estimates. Learn more about adding and subtracting decimals to hundredths: Adding and subtracting decimals to hundredths · Learn more about multiplying decimals to hundredths · Learn more about dividing decimals to hundredths
Sample questions to try together
These are real questions from our 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
Amara's family packs rice for a food bank in bags of 1.5 kilograms. How many kilograms of rice are in 10 bags?
- 0.15 kilograms
- 15 kilograms
- 11.5 kilograms
How you can help
- Figure out a big total together, like 24 cans of juice at $1.15 each or 12 packs of 125 sheets of paper. Estimate first, then multiply.
- Use money to explore powers of 10: what are 10 × $0.25, 100 × $0.25, and 1,000 × $0.25? Talk about how each digit moves.
- Find the area of a rug or a doormat measured in decimal meters, like 1.5 by 2.4. Ask your child to estimate before multiplying.
Where kids can get stuck
- Mixing up carried digits, adding a carry from multiplying by the ones digit into the row for the tens digit.
- Dropping a zero from a number that already ends in one, so 60 × 1,000 comes out as 6,000 instead of 60,000.
- Counting decimal places wrong in a product, so 0.3 × 0.4 comes out as 1.2 instead of 0.12.
Practice makes perfect
Bobby's Math Club has practice problems that adapt to your child’s level, each with a detailed explanation and an easy-to-follow video, so your child can build confidence in these skills one step at a time.
Words your child will hear
- factor
- A number that is multiplied by another number.
- product
- The answer to a multiplication problem.
- partial product
- Part of a multiplication answer, found by multiplying one place at a time.
- algorithm
- A step-by-step method for solving a problem, like the usual way to multiply on paper.
- power of 10
- A number like 10, 100 (10 × 10), or 1,000 (10 × 10 × 10), made only of 10s multiplied together.
- exponent
- A small raised number that tells how many 10s to multiply together, as in 10³ = 10 × 10 × 10.
- decimal point
- The dot that separates the whole number from the parts of a whole.
- estimate
- A close guess found by rounding or using easy numbers.
Ready to build your child’s confidence with multiplying whole numbers and decimals?
In Bobby's Math Club, your child practices these skills at just the right level, with a hint when they need one, a clear explanation after every question, and kid-friendly videos. Unlimited practice is free.
Join the club
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.
Which math standards does Math Expressions Grade 5 Unit 4 cover?
Math Expressions Grade 5 Unit 4 covers these math standards. Each one links to what it means, sample questions, and teaching strategies.
For teachers: Unit names and order vary between editions and districts, so your school’s own materials have the exact sequence. Learn how Bobby's Math Club can help your students grow.