enVision Mathematics Grade 2, Topic 5: Subtract Within 100 Using Strategies
In this unit, your child subtracts within 100 using mental strategies. They count back by tens and ones on a number line, think of subtraction as adding on, and break numbers apart, such as solving 63 − 28 as 63 − 30 + 2. They also solve story problems. It follows the adding work and comes just before the written method for subtracting.
By Robert “Bobby” BarnettMath teacher, parent, and founder of Bobby’s Math Club
What is my child learning in Topic 5?
- Solving subtraction story problems, including comparing two amounts, by drawing a bar model and writing an equation. Learn more: One- and two-step story problems within 100
- Subtracting within 100 by counting back on a number line, adding on from the smaller number, or using a friendly ten. Learn more about adding within 100: Adding within 100 · Learn more about subtracting within 100
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
What is 80 minus 20?
- 50
- 60
- 70
How you can help
- Ask how many minutes are left in a 60-minute show when 42 minutes have passed, and let your child count up from 42.
- Count back by tens together on a walk, from 94 down to 4, then try another start like 87 and ask your child which digit stays the same.
- Compare two books at bedtime: "This one has 64 pages and that one has 38. How many more pages?" Ask your child to show the jumps on a quick number line.
Where kids can get stuck
- Subtracting the smaller digit from the larger in each place, so 63 − 28 becomes 45.
- Taking away 30 instead of 28, then subtracting the extra 2 again instead of adding it back.
- Adding the two numbers in a compare story because it says "more," instead of finding the difference.
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
- difference
- The answer when you subtract; it also tells how much more one amount is.
- number line
- A line with numbers in order at equal spaces, used to count, add, and subtract.
- count back
- Subtracting by counting down from a number, like 52, 51, 50.
- tens
- Groups of 10. In 47, the 4 means 4 tens, or 40.
- ones
- Single units. In 47, the 7 means 7 ones.
- compare
- To decide which is more, less, longer, or shorter, and by how much.
- equation
- A number sentence with an equal sign, like 9 + 4 = 13.
- unknown
- The missing number in a problem, often shown with a box or a question mark.
Ready to build your child’s confidence with subtracting within 100?
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 enVision Mathematics Grade 2 Topic 5 cover?
enVision Mathematics Grade 2 Topic 5 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.