6th Grade Math Textbook, Progress

Use Formulas

4-8

Use the Distance formula, d 5 rt, to complete.

1. d
   mi 2. d
   11.7 mi 3. d
   227.5 km
   r
   55 mph r
   3.9 mph r
   kph
   t
   5 h t
   ? h t
   3.5 h

?

?

A formula is a rule that describes a mathematical

relationship involving two or more quantities. It gives

a simplified way of solving a particular problem.

Each variable in the formula represents a part of

the problem.

A car travels 55 miles per hour. If the distance

between two cities is 330 miles, how long does

it take the car to travel this distance?

To find how long the car travels, use the

Distance formula.

To solve a problem using a formula:


Write the formula that will solve the problem.


Substitute the numbers given in the problem.


Solve for the unknown variable.

It takes the car 6 hours to travel 330 miles.

Study these examples.

d
rt

330 mi 
55 mpht




6 
t

t 
 6 h

55 t

55

330

55

Volume formula:

Volume 
length width height

V 
 
  w  h

Solve for height, h, when V
12 m^3 ,



4 m, and w 
1.5 m.

V 

 w h

12 
 4 1.5h

12 
 6 h

2 
h h
2 m

Perimeter formula:

Perimeter 
twice the sum of length and width

P
2(
w)

Solve for Perimeter, P, when 

 8 in.

and w
6 in.

P
2(
w)

P
2( 8  6 )

P
2(14)

P
 28 P
28 in.

Distance formula:

distance 
 rate  time

d 
 r  t

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