Eureka Math Grade 1, Module 4: Place Value Comparison Addition and Subtraction to 40
In this unit, first graders work with numbers to 40 using place value, the idea that a digit's spot tells what it is worth. They see numbers as tens and ones, compare them, find 10 more and 10 less, and add and subtract using tens. After measuring lengths as numbers in the last unit, this deepens number sense, and next they explore shapes and equal parts.
By Robert “Bobby” BarnettMath teacher, parent, and founder of Bobby’s Math Club
What is my child learning in Module 4?
- Counting, reading, and writing numbers to 40, starting from any number and crossing each new ten smoothly. Learn more: Counting, reading, and writing numbers to 120
- Showing numbers to 40 as tens and ones, like 27 as 2 tens and 7 ones. Learn more: Tens and ones in two-digit numbers
- Comparing numbers to 40 by the tens, then the ones, and writing it with >, <, or =. Learn more: Comparing two-digit numbers with >, =, and <
- Adding within 40, like 23 + 9 or 18 + 20, by combining tens with tens and ones with ones. Learn more: Adding two-digit numbers within 100
- Finding 10 more or 10 less than a number to 40, like 26 and 36, in their heads. Learn more: 10 more or 10 less in your head
- Subtracting tens from tens within 40, such as 40 - 20, and explaining it as 4 tens take away 2 tens. Learn more: Subtracting tens, like 70 - 30
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
Count by tens: 10, 20, 30, 40, __. What number comes next?
- 51
- 50
- 60
How you can help
- Count pieces of pasta into cups of ten, with a few left loose, to make a number up to 40. Ask how many tens and ones there are, then add 10 more.
- Compare two numbers on a walk or at the store, like 27 and 32, and ask which is greater and how the tens helped them decide.
- Pose an adding puzzle at dinner: "You have 23 stickers and get 9 more. How many now?" Encourage making a ten from the 3 and some of the 9.
Where kids can get stuck
- Saying "29, 20-10" instead of 30 when crossing into a new ten.
- Showing 27 as 2 cubes and 7 cubes, forgetting the 2 means 2 tens.
- Writing 25 for 23 + 20, adding the 2 tens as if they were 2 ones.
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
- place value
- What a digit is worth because of its spot, like the 4 in 42 meaning 40.
- tens
- Groups of ten. In 34, there are 3 tens.
- ones
- Single things not in a group of ten. In 34, there are 4 ones.
- digit
- One of the symbols 0 to 9 used to write numbers.
- greater than
- The symbol > means the first number is bigger, like 9 > 4.
- less than
- The symbol < means the first number is smaller, like 4 < 9.
- 10 more
- The number you get by adding one ten, like 46 to 56.
- 10 less
- The number you get by taking away one ten, like 46 to 36.
- sum
- The answer when you add, like 7 in 3 + 4 = 7.
Want to help your child master numbers to 40?
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 Eureka Math Grade 1 Module 4 cover?
Eureka Math Grade 1 Module 4 covers these math standards. Each one links to what it means, sample questions, and teaching strategies.
- 1.NBT.A.1: Count to 120, starting at any number.
- 1.NBT.B.2: Understand that the two digits of a two-digit number represent amounts of tens and ones.
- 1.NBT.B.3: Compare two two-digit numbers.
- 1.NBT.C.4: Add within 100.
- 1.NBT.C.5: Given a two-digit number, mentally find 10 more or 10 less.
- 1.NBT.C.6: Subtract multiples of 10 in the range 10-90.
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.