Use a Number Line to Catch a Thief
It’s a case for the Odd Squad: a thief is stealing objects from the Trophy Room, and only with subtraction sleuthing skills, a number line, and a secret gadget from the Odd Squad’s lab will agents be able to figure out “whodunit,” crack the case and put things right again.
Materials
Directions
Explain to your child that today, you’ll be exploring subtraction. Before you begin, create a sample number line with the” Odd Squad Number Line-inator” printable. Next, write the numbers 1-10 on the index cards (one number per card). Finally, prepare the case file by cutting out and attaching the logo to the manila folder.
Let your child know that you’ve received a letter from the head of Odd Squad, Ms. O. Explain that The Odd Squad needs our help. Are they ready to crack a math case? Read the letter from Ms. O aloud.
Move to “Casework,” then celebrate with a “Case Closed” learning recap.
Letter From Ms. O
Agents! There you are! Something very odd has happened. The town’s oddest objects are all in danger. Nobody panic, but someone with a love of “odd” has been taking treasures from the Trophy Room. There are only 10 items left in our collection, and the thief is still at it. Next time this sneaky suspect steals our stash, you’ll need to do some sleuthing to figure out which visitor has been leaving with our most prized possessions. All we know is, he or she seems to be stealing his favorite number of items each time. So, are you on the case? Then hurry, because Odd Squad needs you!
Casework
Explain that in order to crack “The Case of the Trophy Room Bandit,” your child will need to know how to subtract numbers from 10. Say: “Subtraction means taking something away — exactly as this sneaky visitor has done!”
Help your child to make a Number Line-inator to use against the Trophy Room Bandit!
Demonstrate how to use the Number Line-inator. Write the equation 10 - ___ = 6 on the board. Place the arrow over the 10, then move the arrow to the 6, counting how many numbers you go back: 9, 8, 7, 6. Show your child that you went back four spaces or numbers, which means 10 - 4 = 6. Write up a few more subtraction equations for the children to figure out.
Now have your child place 10 beans or chips in his bag and close his eyes. Then steal a few of the beans/chips. Now have your child open his eyes and use the number line to figure out how many beans were taken by subtracting the amount remaining from the number 10. Continue playing this game, consider taking turns stealing. Experiment with the number line in other ways by starting with fewer than 10 objects. Have your child write out each subtraction equation that was solved on the back of the paper bag.
Case Closed
Tell your child: “Great work, agent! Looks like we nabbed all of the mystery thieves. As part of our training, we like to review what we learned from the case and enter it in the case file so that future agents-in-training can learn from it.”
Ask: “What did we learn about subtraction? What are some tools or strategies we can use to help us solve subtraction problems? What are some examples of subtraction equations?”
Write down the findings that your child shares, close your case file and write CASE CLOSED across the front. Congratulate your agent on a case well-solved.
Math