Video solutions to help Grade 8 students learn how to define constant rate in varied contexts as expressed using two variables where one is t
representing a time interval.

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Lessons for Grade 8

Common Core For Grade 8

• Students know the definition of constant rate in varied contexts as expressed using two variables where one is t
representing a time interval.

• Students graph points on a coordinate plane related to constant rate problems.

• When constant rate is stated for a given problem, then you can express the situation as a two variable equation.
The equation can be used to complete a table of values that can then be graphed on a coordinate plane.

Example 1

Pauline mows a lawn at a constant rate. Suppose she mows a 35 square foot lawn in 2.5 minutes. What area, in square feet, can she mow in 10 minutes? t minutes?

Example 2

Water flows at a constant rate out of a faucet. Suppose the volume of water that comes out in three minutes is 10.5 gallons. How many gallons of water comes out of the faucet in t minutes?

Exercises 1–3

1. Juan types at a constant rate. He can type a full page of text in 3 1/2 minutes. We want to know how many pages, p, Juan can type after t minutes.

a. Write the linear equation in two variables that represents the number of pages Juan types in any given time interval.

b. Complete the table below. Use a calculator and round answers to the tenths place.

c. Graph the data on a coordinate plane.

d. About how long would it take Juan to type a 5-page paper? Explain.

2. Emily paints at a constant rate. She can paint 32 square feet in five minutes. What area, A, can she paint in t minutes?

a. Write the linear equation in two variables that represents the number of square feet Emily can paint in any given time interval.

b. Complete the table below. Use a calculator and round answers to the tenths place.

c. Graph the data on a coordinate plane.

d. About how many square feet can Emily paint in 2 1/2 minutes? Explain.

3. Joseph walks at a constant speed. He walked to the store, one-half mile away, in minutes. How many miles, m, can he walk in t minutes?

a. Write the linear equation in two variables that represents the number of miles Joseph can walk in any given time interval, t.

b. Complete the table below. Use a calculator and round answers to the tenths place. c. Graph the data on a coordinate plane.

d. Joseph's friend lives miles away from him. About how long would it take Joseph to walk to his friend's house? Explain.