Zearn Math Grade 1, Mission 4: Place Value, Comparison, Addition and Subtraction to 40
In this unit, your child works with numbers to 40, using tens and ones to count, compare, add, and subtract. They find 10 more and 10 less, add numbers like 27 + 6, and subtract tens. This builds on the measurement unit and leads into a geometry unit about building and splitting shapes.
By Robert “Bobby” BarnettMath teacher, parent, and founder of Bobby’s Math Club
What is my child learning in Mission 4?
- Solving story problems within 20, including ones about comparing two amounts, using drawings with tens and ones. Learn more: Adding and subtracting story problems within 20
- Counting and writing numbers to 40, starting from any number and moving smoothly across each new ten. Learn more: Counting, reading, and writing numbers to 120
- Showing numbers to 40 as tens and ones, like 32 as 3 tens and 2 ones. Learn more: Tens and ones in two-digit numbers
- Comparing numbers to 40, like 23 and 32, by checking tens first, and writing >, <, or =. Learn more: Comparing two-digit numbers with >, =, and <
- Adding within 40, like 27 + 6 or 14 + 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 up to 40, such as 25 becoming 35 or 15. Learn more: 10 more or 10 less in your head
- Subtracting tens within 40, like 40 - 20, by thinking 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
I had some toy cars. My friend gave me 3 more cars. Now I have 8 cars in total. How many toy cars did I have at first?
- 3
- 5
- 8
How you can help
- Count 30 to 40 cereal pieces into groups of ten. Ask how many tens and ones, then add 6 more and see if a new ten forms.
- Pick two jersey numbers or page numbers under 40, like 23 and 32, and ask your child which is greater and why.
- Count by tens from a starting number on a walk, like 7, 17, 27, 37, and ask which digit changes each time.
Where kids can get stuck
- Writing 27 + 6 as 213, putting the 13 ones beside the 2 tens instead of making a new ten.
- Deciding 19 is greater than 31, because 9 is more than 1.
- Counting 28, 29, 20 instead of moving on to 30.
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
- tens
- Groups of ten. In 34, the 3 means 3 tens.
- ones
- Single units. In 34, the 4 means 4 ones.
- place value
- What a digit is worth because of where it sits, like the 5 in 52 meaning 50.
- new ten
- Ten ones grouped together to make one ten when adding.
- 10 more
- The number you get by adding one ten, like 47 to 57.
- 10 less
- The number you get by taking away one ten, like 47 to 37.
- greater than (>)
- A symbol that means the first number is bigger, as in 52 > 25.
- less than (<)
- A symbol that means the first number is smaller, as in 19 < 31.
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 Zearn Math Grade 1 Mission 4 cover?
Zearn Math Grade 1 Mission 4 covers these math standards. Each one links to what it means, sample questions, and teaching strategies.
- 1.OA.A.1: Use addition and subtraction within 20 to solve word problems.
- 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.