Zearn Math Grade 2, Mission 1: Sums and Differences to 100
In this unit, your child adds and subtracts within 100 using mental strategies. They make a ten, add and take away tens, and solve one- and two-step story problems. These quick strategies set up the rest of the year. Next, your child uses the same skills to add and subtract lengths measured in centimeters.
By Robert “Bobby” BarnettMath teacher, parent, and founder of Bobby’s Math Club
What is my child learning in Mission 1?
- Solving story problems within 100, like how many stickers are left, and showing them with a tape diagram or an equation. Learn more: One- and two-step story problems within 100
- Adding and subtracting within 100 in their heads, such as 38 + 7 by making a ten, or 64 - 20 by taking away tens. 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
- Add on a walk or ride: start at 38 and ask what 7 more makes. Talk about making 40 first, then adding the other 5.
- Tell a story at snack time: 'There were 24 crackers and we ate 9. How many are left?' Ask your child to show it with a quick drawing.
- Count back by tens from a number like 64: 54, 44, 34. Then ask what 64 - 20 is and how your child knew so quickly.
Where kids can get stuck
- Counting by ones for 38 + 7 instead of using 2 to make 40 and adding the other 5.
- Mixing up tens and ones, so 64 - 20 becomes 62 instead of 44.
- Adding whenever a story says 'more,' as in 'Ava has 52 stamps, 17 more than Leo,' where Leo has 35.
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
- tape diagram
- A drawing of long bars, like strips of tape, that shows the parts of a story problem.
- sum
- The answer when you add. In 8 + 5 = 13, the sum is 13.
- difference
- The answer when you subtract. In 13 - 5 = 8, the difference is 8.
- make a ten
- A strategy that fills a ten first, so 9 + 5 becomes 10 + 4.
- tens
- Groups of ten. The 4 in 45 means 4 tens, or 40.
- ones
- Single units. The 5 in 45 means 5 ones.
- equation
- A number sentence with an equal sign, like 13 - 5 = 8.
Want to help your child master adding 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 Zearn Math Grade 2 Mission 1 cover?
Zearn Math Grade 2 Mission 1 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.