Illustrative Mathematics Grade 1, Unit 4: Numbers to 99
In this unit, first graders learn that numbers to 99 are made of tens and ones, so 47 means 4 tens and 7 ones. They count and write these numbers, compare them with >, <, and =, and find 10 more and 10 less. It builds on using ten to add within 20 in the last unit, and next they add numbers within 100.
By Robert “Bobby” BarnettMath teacher, parent, and founder of Bobby’s Math Club
What is my child learning in Unit 4?
- Counting groups of objects by tens and ones and writing the matching numbers up to 99. Learn more: Counting, reading, and writing numbers to 120
- Representing two-digit numbers with tens and ones, so 47 is 4 tens and 7 ones, or 40 and 7. Learn more: Tens and ones in two-digit numbers
- Comparing two-digit numbers by looking at the tens first, and writing comparisons with >, <, or =. Learn more: Comparing two-digit numbers with >, =, and <
- Finding 10 more or 10 less than a two-digit number and noticing that the ones digit stays the same. Learn more: 10 more or 10 less in your head
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 a big pile of pasta into small cups of ten together. Ask how many tens and ones there are, and write the number.
- Play "10 more" by adding a cup of ten to the pile, and ask for the new number before counting. Then try taking a cup away.
- Compare two numbers on signs or packages and ask which is greater and why. Write it with > or < on a scrap of paper.
Where kids can get stuck
- Counting "47, 48, 49, 40" instead of moving on to 50.
- Saying 10 more than 47 is 48, changing the ones instead of the tens.
- Writing 74 for 4 tens and 7 ones, flipping the digits.
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, 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.
- place value
- What a digit is worth because of its spot, like the 4 in 42 meaning 40.
- 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.
Ready to build your child’s confidence with numbers to 99?
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.
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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.
Which math standards does Illustrative Mathematics Grade 1 Unit 4 cover?
Illustrative Mathematics Grade 1 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.