Lesson 17

This Number Talk encourages students to use their experiences counting coins and skip counting by 10 and 5 to add within 100. The understandings elicited here will be helpful in later lessons when students solve money problems with amounts including dollars and cents.

• Display one expression.
• “Give me a signal when you have an answer and can explain how you got it.”
• 1 minute: quiet think time

• Record answers and strategies.
• Keep expressions and work displayed.
• Repeat with each expression.

• “How could these expressions help us think about solving money problems?” (It’s like adding quarters, dimes, and nickels.)

The purpose of this activity is for students to find coin combinations that have a value of 100 cents and make connections between coin collections that have the same value. They are invited to connect the value of nickels to dimes and relate their understanding of place value to represent 100 cents with dimes (MP7). In the next activity, students learn that 100 cents is the same as a dollar.

• Display the money poster where students can see it to check coin values.

• Groups of 2

• “Today, we will continue our work with money.”
• “For each set of coins, identify the coin and count to see how many coins are in the collection.”
• “Then find the total value of the coins using a method that makes sense to you.”
• 8 minutes: independent work time
• “Compare with a partner.”
• 4 minutes: partner discussion

• “How could you use what you know about nickels to figure out how many dimes you needed?” (For every 2 nickels we needed 1 dime.)
• “How many pennies would you need in order to have the same value? Explain.” (100 because a penny is worth 1 cent, so you need 100 to make 100 cents.)
• “What do you notice about each coin collection? What do you wonder?” (I notice it takes more nickels to have the same value than quarters or dimes. It only takes 4 quarters. It takes 10 dimes just like it takes 10 tens to make 100. Is 100 cents the same as a dollar? 

The purpose of this activity is for students to find combinations of coins with a value of 100 cents and understand that a dollar is the same as 100 cents. They add within 100 by grouping like coins, using a ten, or using counting on strategies. They find coin combinations that add up to 100 cents or 1 dollar and write the leftover amount as cents. This work builds on students’ understanding of a hundred.

•   Add a dollar bill to the money poster showing the front and back to display in the launch.

• Groups of 2
• Display the poster with the dollar added.

  

  

• “We just saw that there are many different ways to use coins to make 100 cents. One dollar is also the same as 100 cents.”
• “If I have a dollar and I found a quarter, how much money would I have?” (125 cents or \$1 and 25¢)
• 30 seconds: quiet think time
• Display a dollar and a quarter and write $1 and 25¢.

  

  

• “When you write dollar amounts you use the \$ symbol. Use the ¢ symbol for the amount that cannot be grouped to make a dollar.”

• “Now, you are going to work with a partner to make dollars and cents.”
• 10 minutes: partner work time
• Monitor for students who show Priya's money in different ways to share in the Lesson Synthesis.

If students show the value of Andre and Han's coins only in cents, consider asking:

• “How did you find the total value of the coins?”
• “How many dollars does _______ have? How many leftover cents would he have?”
• “How could you say how much money _______has using dollars and cents?”

• “I noticed that when you were creating a coin collection for Priya, there were different solutions.”
• “How is it possible that everyone represented the same amount of money?” (Different coins can show the same amount, but you need a different number of coins.)
• Invite students to share different combinations of coins they used to make $1.
• Share and record responses.