Grade by Grade
B. Number · Adding and Subtracting

Adding and Subtracting: Unit Review

B2.1 B2.2 B2.3 B2.4 B2.5About 40 minutes
Learning goals
  • I can add and subtract numbers to 20 using strategies I learned.
  • I can solve story problems up to 50 and explain my thinking.
  • I can make and share equal groups.

Words to know

sum
The answer when you add. In 6 + 2 = 8, the sum is 8.
difference
The answer when you subtract. In 9 − 4 = 5, the difference is 5.
fact family
Adding and subtracting facts that use the same three numbers, like 3 + 5 = 8 and 8 − 5 = 3.
equal groups
Groups that all have the same number of things.

Let's review!

You have learned a lot about adding and subtracting. This review has a few questions from every lesson in the unit. Try each one, then press Show answer to check. If a part feels tricky, go back to that lesson for more practice.

What Adding and Subtracting Mean

1

🐦🐦🐦🐦🐦🐦🐦🐦

8 birds sit on a fence. 3 fly away. Is this adding or subtracting? Solve it.

2

True or false: 7 = 3 + 4

3

Jo has 5 pencils. Ty has 2 pencils. How many more pencils does Jo have?

Addition Facts to 10

1

6 + 2 = ?

2

What number goes with 1 to make 10?

3

🍓🍓🍓🍓🍓 + 🍓🍓🍓

How many strawberries?

945whole on top, parts below4 + 5 = 95 + 4 = 99 − 4 = 59 − 5 = 4
A fact family for 4, 5 and 9. The whole (9) is at the top and the parts (4 and 5) are at the bottom. The same three numbers make two adding facts and two subtracting facts.

Subtraction Facts and Fact Families

1

Write the fact family for 2, 4 and 6.

2

10 − 7 = ?

3

Eli says 8 − 5 = 3. Check by adding. Is he right?

Math Rules: Order, Zero and Adding Three Numbers

1

6 + 0 = ?

2

3 + 8 + 7 = ?

3

True or false: 5 + 2 = 2 + 5

Mental Math: Counting On, Counting Back and Doubles

1

14 + 3 = ?

2

19 − 2 = ?

3

5 + 4 = ? Use a double.

94move 19 + 4 = 10 + 3 = 13
Make ten for 9 + 4: move 1 dot to fill the first ten frame. Now there is 1 full ten and 3 more, so 9 + 4 = 10 + 3 = 13.

Mental Math: Make Ten and Estimate

1

10 + 6 = ?

2

8 + 3 = ? Use make ten.

3

12 − 5 = ?

4

Without solving, is 5 + 4 more or less than 10?

Solving Story Problems up to 50

1

There are 26 books on a library cart. A helper adds 12 more. How many books are on the cart now?

2

40 − 20 = ?

3

Lena had 16 shells. She found some more. Now she has 20. How many did she find?

Equal Groups up to 10

1

4 bowls each have 2 strawberries. How many strawberries in all?

2

Share 6 muffins equally between 2 friends. How many does each friend get?

3

2 pizzas are each cut into 4 equal pieces (fourths). How many pieces in all?

Just for fun

Why did the minus sign feel left out?

It kept getting taken away! (Don't worry, the plus sign added it back.)

How to use this review

  • Do the review over two short sittings if your child gets tired. Each section matches one lesson.
  • Let your child use counters, fingers, a ten frame or a drawing. Using tools is part of Grade 1 math.
  • After each answer, ask "How did you know?" Explaining a strategy matters as much as the answer.
  • Note which section had mistakes, then revisit that lesson's practice and activities.
Check your understanding

Quiz

1.

Max has 4 toques. He gets 3 more. How many toques does he have?

2.

Which numbers are partners of 10?

3.

Which fact is in the fact family for 3, 5 and 8?

4.

What is 8 − 0?

5.

What is 7 + 7?

6.

What is 9 + 5?

7.

What is 29 + 10?

8.

There are 36 kids at the rink. 14 go home. How many kids are still at the rink?

9.

Which shows equal groups?

10.

6 friends each eat one half of a pear. How many pears do they eat?

For parents and teachers

Use mistakes to choose what to revisit. Each review section matches one lesson.

  • Adds when the story says something went away, or can't do "how many more": revisit What Adding and Subtracting Mean. Act out the story with toys.
  • Slow or unsure with facts to 10, or mixes up partners of 10: revisit Addition Facts to 10 and play Make 10 Go Fish.
  • Can add but not subtract, or writes facts like 5 − 2 = 7: revisit Subtraction Facts and Fact Families. Practise "think addition" and checking by adding.
  • Thinks 9 − 0 = 0, or adds three numbers from left to right only: revisit Math Rules: Order, Zero and Adding Three Numbers.
  • Counts the starting number when counting on (7 + 3 = 9), or doesn't know doubles: revisit Mental Math: Counting On, Counting Back and Doubles.
  • Counts every dot for sums like 9 + 5, or can't tell if an answer makes sense: revisit Mental Math: Make Ten and Estimate.
  • Mixes up tens and ones, or picks the wrong operation in story problems: revisit Solving Story Problems up to 50. Use bundles of 10 straws.
  • Groups that are not the same size, or trouble with halves and fourths: revisit Equal Groups up to 10. Share real snacks.

A few mistakes are normal. Praise the strategy your child explains, not only the right answer.