Lesson 10 Math

Make a Ten

Standard

• KY.2.OA.2 Fluently add and subtract within 20 using mental strategies.

Learning Objectives

• Students will demonstrate how to rewrite a problem to make a ten.

• Students will calculate problems that add up to 20.

How to Make a Ten

• Change one addend to 10 in order to solve the problem

• Example: 9 + 4 = 13 can be changed to 10 + 3 = 13

• You are adding 1 to 9 to make it ten and subtracting 1 from 4 to make it 3

Practice Problem 1

• How would you rewrite 8 + 6 to make a ten?

• Step 1: Add 2 to 8 to make it 10

• Step 2: Subtract 2 from 6 to make it 4

• Side note: Adding 2 to 8 and subtracting 2 from 6 evens out the problem

• Step 3: Rewrite as 10 + 4

• Step 4: Solve to see that 8 + 6 = 14, and 10 + 4 = 14 as well

Practice Problem 2

• How can we change 9 + 6 to make a ten?

• Step 1: Add 1 to 9 to make it 10
  

• Step 2: Subtract 1 from 6 to make it 5
  

• Step 3: Rewrite as 10 + 5
  

• Step 4: Solve to see that 9 + 6 = 15, but 10 + 5 = 15 as well

Multiple Choice

How would you rewrite 8 + 4 to make a ten?

• 10 + 4

• 10 + 2

• 8 + 2

Multiple Choice

How would you rewrite 9 + 8 to make a ten?

• 10 + 7

• 10 + 8

• 9 + 10

Fill in the Blanks

Rewrite 8 + 5 to make a ten and give me the solution.

Multiple Choice

True or False: 8 + 3 is the same as 10 + 1

• True

• False

Multiple Choice

True or False: 9 + 5 is the same as 10 + 3

• True

• False