# Lesson 10 Addition and Subtraction With a Ten

• Let’s add and subtract with teen numbers.

## Warm-up Number Talk: A Ten and Some Ones

Find the value of each expression mentally.

## Activity 1 Story Problems With a Ten

1. Kiran has a collection of 5 baseball caps.
He gets some more baseball caps for his birthday.
Now he has 15 baseball caps all together.
How many baseball caps did he get?
Show your thinking using drawings, numbers, or words.

Equation:

Equation:

2. Priya has a comic book collection.
She gets 3 new comic books.
Now she has 13 comic books.
How many comic books did she have to start?
Show your thinking using drawings, numbers, or words.

Equation:

Equation:

## Activity 2 Related Equations

Mai is finding the missing number in .

She says, “I can use what I know about 10 and some ones to help.”

What does Mai mean?

Find the number that makes each equation true.
Show your thinking using drawings, numbers, or words.

## Problem 1

1. Find the number that makes each equation true.

2. How are the 2 equations the same? How are they different?