3.MD.7 Unknown Side Area with Partners
Objective
Common Core: 3.OA.3 Use multiplication and division within 100 to solve word problems in situations involving … arrays …
Specific/Student Friendly: Students will create arrays and, knowing the areaand one side, divide to find the unknown side of a rectangle
Materials Needed
Missing Side Areasheets, Sheet A for half the class, and Sheet Bfor the other half.
Color tiles or grid paper
Teacher Input
- Ask: How can we find anunknown side when we know an area and one side of a rectangle? (Answer: Divide the area by the side you know or create the rectangular array and count the units of the unknown side)
Guided Practice
- Demonstrate, using student input, using both arrays and division to find the unknown width of a rectangle with an area of 24 and a width of 3.
Independent Practice
- Student partners work together to find missing sides on the Unknown Side Area sheets. Student A is given the area and the Student B is given the length. Students share their information, then they both find the unknownwidth; Student A by creating an array and Student B by dividing.
- Students share their solutions with their partners and check for mistakes should their solutions differ. Students then switch roles for the next problem, and continue to switch each subsequent problem.
Check for Understanding
- Check that students are creating accurate arrays and using valid division strategies. Debrief whole class at the end of the activity to share struggles and confusions students may have had and how they resolved them.
Unknown Side Area Sheet A
My Name______Partner’s Name ______
1.The area of a rectangle is 48 square units. Ask your partner for the length, create the rectangle, and find the width.
Area = 48 units2 Length =______Width =______
Compare answers with you partner, and complete the equations below:
48 ÷ ____ = ____
____ x ____ = 48
2.The length of a rectangle is 8 units. Ask your partner for the area, and divide to find thewidth.
_____÷8= ____
Area = ______Length = 9 units Width =______
Compare answers with you partner, and complete the equation below:
8 x ____ = _____
3.The area of a rectangle is 40 square units. Ask your partner for the length, create the rectangle, and find the width.
Area = 40 units2 Length =______Width =______
Compare answers with you partner, and complete the equations below:
40÷ ____ = ____
____ x ____ = 40
4.The length of a rectangle is 9 units. Ask your partner for the area, and divide to find thewidth.
_____÷9 = ____
Area = ______Length = 9 units Width =______
Compare answers with you partner, and then complete the equation below:
9 x ____ = _____
Unknown Side Area Sheet B
My Name______Partner’s Name ______
1.The length of a rectangle is 8 units. Ask your partner for the area, and divide to find thewidth.
_____÷8 = ____
Area = ______Length = 8 units Width =______
Compare answers with you partner, and complete the equation below:
8 x ____ = _____
2.The area of a rectangle is 32 square units. Ask your partner for the length, create the rectangle, and find the width.
Area = 32 units2 Length =______Width =______
Compare answers with you partner, and complete the equations below:
32÷ ____ = ____
____ x ____ = 32
3.The length of a rectangle is 8 units. Ask your partner for the area, and divide to find thewidth.
_____÷8= ____
Area = ______Length = 8 units Width =______
Compare answers with you partner, and complete the equation below:
8 x ____ = _____
4.The area of a rectangle is 36 square units. Ask your partner for the length, create the rectangle, and find the width.
Area = 36 units2 Length =______Width =______
Compare answers with you partner, and complete the equations below:
36÷ ____ = ____
____ x ____ = 36
MathScience360.org