Determine a missing dimension given the area and one dimension
Objectives
Student will be able to:
draw a diagram for a given situation.
calculate a missing dimension given the area and one dimension of a rectangle.
Introduction
Marcel wants to put a new rectangular garden that is 90 square feet on the side of his gardening shed. His gardening shed is 10 feet long. If he wants the garden to be the same length as his shed, how wide should he make the garden so it has a total area of 90 square feet?
First draw a diagram of the the shed and new garden.
The formula to find the area of a rectangle is:
This formula can be rewritten to find the length and width as:
or
The area of the garden is to be 90 square feet with a length of 10 feet.
Substitute these numbers into the formula to find the width and solve.
Marcel should make his garden 9 feet wide.
Examples
1.
Paulina wants to enter a painting in a local contest. The rules state that all paintings must be 6 square feet. Paulina's painting canvas is 2 feet wide. How long should her canvas be to meet the rules of the contest?
Draw a diagram of Paulina's canvas.
Paulina's canvas is 2 feet wide and has an area of 6 square feet.
2.
Use the diagram to write an equation and solve to find how long Paulina's canvas should be.
The area of the painting is 6 square feet and the width is 2 feet.
Paulina's canvas should be 3 feet long.
Try Together
Complete the exercises.
1.
A television screen is advertised to be 330 square inches. A sales person measures the length to be 22 inches. Draw a diagram to represent the television screen. Label the length, width, and area.
Check student's diagram.
2.
A television screen is advertised to be 330 square inches. A sales person measures the length to be 22 inches. What is the width of the screen?
The television screen is 15 inches wide.
3.
A rectangle has an area of 56 square cm. The width of the rectangle is 7 cm. What is the length of the rectangle? Draw a diagram and solve.
The length of the rectangle is 8 cm.
Please evaluate the student's answers:
Excellent
Good
Okay