Lesson objective: Apply skip counting to mentally adding five and ten dollars.

This lesson provides an opportunity for students to apply their knowledge and understanding of a real-life mathematical situation. Students are asked to mentally calculate the amount of money Kareem earns from his Canine Care business.

Key Concept students will use:

- skip counting to add or subtract because, when we count, we move along the number line.

Skills students will use:

- Adding multiples of ten (1.NBT.C.4) (1.NBT.C.5)
- Using understanding of place value to add and subtract (1.NBT.C.5) (1.NBT.C.6)
- Understanding three-digit numbers

Students engage in Mathematical Practice 8 (Look for and express regularity in repeated reasoning) as they notice the repeated pattern when skip counting and how this helps them mentally add or subtract numbers using numerical reasoning. An open number line is used to assist students to mentally add five and ten dollars.

**Key vocabulary: **

- decompose
- open number line