Chapter 4, Lesson 8Rate-Time-Distance Problems

By:A. s.

Objective:To solve word problems involving

uniform motion.

An object is in uniform motion when it moves

without changing its speed, or rate.

Example:Two jets leave Denver at 9:00 A.M.,

one flying at a speed 50 km/h greater than the other which is

traveling west. At 11:00 A.M., the planes are 2500 km apart. Find

their speeds.

Step 1:

Explore:The problem asks for the jets’ speeds.

Step 2:

Assign VariablesX=Jet 1’s Speed, and X+50=Jet2’s speed because it is flying 50km/h faster than jet 1.

Step 3:

Plan:

Write an equation

2x+2=2(x+50)=2500

  Rate x Time = Distance

Jet 1 x 2 2x

Jet 2 x+50 2 2(x+50)

Step 4

Solve:2x+2(x+50)=25002x+2x+100=2500

4x+100=25004x=2500-100

4x=2400X=600=Jet 1

X+50=650=Jet 2

Step 5:

Check and write your answer in a sentence.

Jet 1 is flying at a rate of 600 km/h, and Jet 2 is flying at 650 km/h.