Grade: 3, Topic(s): addition/subtraction, money

## Purpose

To subtract 12 from any number using mental computation.

Shorthand pictures of coins, such as , , , or

To begin this adding and subtracting activity, write

On the board. To explain the symbols, you can point to the letters one by one as you say, “dollar, dime, dime, penny, penny, penny.” Then ask children how much this amount is worth. **$1.23.** If children have difficulty, you can have them add each amount by counting on as you point to each letter. (One dime is 10¢, another makes 20¢, and so on.)

Now add or erase one P, N, or D. Ask a student how much the new collection is worth. Continue adding or taking away one coin or one bill at a time and choosing a student to respond. Encourage children to watch as you change the symbols on the board, and to work from the previous amount rather than recalculate from the beginning.

Part 1 has children working with a collection of dollars, dimes, and pennies (hundreds, tens, and ones). Part 2 includes nickels – followed by the extension, which incorporates quarters.

I’m going to draw… Dollar, Dime, Dime, Penny, Penny, Penny. What is the total value of this collection? ($1.23)

Draw (using shorthand notation):

- Dollar, dime, dime, penny, penny, penny

*If children need more practice or are enjoying their mastery, repeat drawing other collections of dollars, dimes, and pennies using shorthand notation. If children are ready to move on, go to Part 2.*

Now I’m going to draw one more dollar. What is the total value now? (Then add nickels, one at a time, and ask children the total value after each addition.)

Draw (using shorthand notation):

- Dollar (total now: $2.23)
- Nickel (total now: $2.28)
- Nickel (total now: $2.33)
- Nickel (total now: $2.38)
- Nickel (total now: $2.43)
- Nickel (total now: $2.48)

*If children need more practice, repeat by adding dollars, dimes, nickels, and pennies to an existing collection of dollars and cents. Or, when children seem excited for a new challenge, move on to the extension.*

Now I’m going to add two dollars. What is the total value now? Let’s add a quarter. What is the value now? Let’s erase three pennies. (Continue adding coins to the collection and erasing coins as desired.)

Draw (using shorthand notation):

- Dollar ($3.48)
- Dollar ($4.48)
- Quarter ($4.73)

Erase

- Penny ($4.72)
- Penny ($4.71)
- Penny ($4.70)

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