Zearn Math Grade 1, Mission 2: Introduction to Place Value Through Addition and Subtraction Within 20
In this unit, your child adds and subtracts within 20 and starts to see teen numbers as a ten and some ones. Making a ten becomes a key strategy, so 9 + 5 turns into 10 + 4. This builds on last unit's facts to 10 and leads into comparing and measuring length.
By Robert “Bobby” BarnettMath teacher, parent, and founder of Bobby’s Math Club
What is my child learning in Mission 2?
- Solving adding and subtracting stories within 20 and writing an equation that matches each story. Learn more: Adding and subtracting story problems within 20
- Adding three numbers in a story, like 4 + 6 + 3, by finding two that make 10 first. Learn more: Story problems that add three numbers
- Changing the order or grouping of addends, the numbers being added, so a ten is easier to make. Learn more: Adding in any order to make it easier
- Adding and subtracting within 20 by making a ten or taking from ten, as in 9 + 5 = 10 + 4. Learn more about adding within 20: Adding within 20 · Learn more about subtracting within 20
- Seeing teen numbers as one ten and some ones, so 14 is a ten and 4 ones. Learn more: Tens and ones in two-digit numbers
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
- Fill two rows of five boxes drawn on paper with cereal pieces to make 10, then add more. Ask your child to name the number as a ten and some ones.
- Ask a three-number question on a walk or ride, like "7 red, 3 blue, and 5 white flowers. How many in all?" Notice if your child adds 7 and 3 first.
- Practice taking from ten at dinner: for 15 - 9, take 9 from the 10 to leave 1, then add the 5 extra ones to get 6.
Where kids can get stuck
- Writing fourteen as 41, because the word starts with the sound of four.
- Breaking apart the wrong addend when making a ten, so 9 + 5 gets stuck.
- Counting all the objects from 1 in a three-number story, instead of grouping to make a ten.
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
- addend
- One of the numbers you add together, like 4 and 3 in 4 + 3.
- make a ten
- Break apart a number so one part fills a ten, like 8 + 5 = 8 + 2 + 3.
- tens
- Groups of ten. In 34, the 3 means 3 tens.
- ones
- Single units. In 34, the 4 means 4 ones.
- total
- How many there are altogether.
- equation
- A number sentence with an equal sign, like 6 + 2 = 8.
- strategy
- A plan or shortcut for solving a problem.
Ready to build your child’s confidence with adding within 20?
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 Zearn Math Grade 1 Mission 2 cover?
Zearn Math Grade 1 Mission 2 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.OA.A.2: Solve word problems that call for addition of three whole numbers.
- 1.OA.B.3: Apply properties of operations as strategies.
- 1.OA.C.6: Add and subtract within 20.
- 1.NBT.B.2: Understand that the two digits of a two-digit number represent amounts of tens and ones.
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.