# The Ten Monster

Here comes the Ten Monster! Get ready to learn about subtracting tens in this hands-on lesson.

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Students will be able to calculate ten less than numbers under 20.

(5 minutes)
• Show students a tower of 15 snap cubes.
• Ask, “How many cubes do I have in my tower?”
• Count aloud with students.
• Now ask, “How many cubes would I have if I had 10 less?”
• Have students share a few answers, then take away 10 cubes.
• Count how many are left.
(5 minutes)
• Write on the board 15-10 = 5. Tell students that 15 take away ten is five.
• Point to the number 15 on the number chart. Move your finger to the space directly above 15 (5) and say 15-10=5.
• Remind students that the one in “15” means that the number has one ten.
• When you take away the ten (by subtracting) there are only five ones left.
(10 minutes)
• Hand out snap cubes to the students. Have them each make a tower of 17 cubes.
• Now tell them that a Ten Monster is coming to town. The Ten Monster loves to eat parts of numbers. He takes one ten from each number.
• Ask students to figure out how many cubes their towers would have if the Ten Monster came and took ten cubes.
• After students solve the problem, have them turn to a partner to share out their answers.
• Have students turn back to the number chart to see that ten less than 17 is 7.
(15 minutes)
• Pass out Here Comes the Ten Monster! and Ten Less worksheets.
• Have students work independently on the worksheets, circulating around the room to provide assistance as needed.

Enrichment:Have students create their own “Ten Monster” problems and ask them to trade problems with a partner.

Support:Have students complete the worksheets with the help of snap cubes and/or number charts.

(5 minutes)
• Assess students’ understanding by observing how they are subtracting by ten. Are they able to subtract without counting objects one-by-one?
• Assess understanding by looking at students’ completed worksheets.
(5 minutes)

Have students share some of their answers to the Here Comes the Ten Monster worksheets.