6th Grade Math Textbook, Progress

Find the Original Number

12-5

25% of Marlo’s savings is in a shoebox

under her bed. The shoebox has $45 in

it. How much has Marlo saved in all?

Let s
total savings.

25% of s
$45

s
$45

s 
$45

s
$180

Marlo has saved $180 in all.

4

1

4

1

1

4

1

4

percentage
ratebase p
rb

original number (total number)

Write and solve a proportion.

45 b
 900

45 b  45 
 900  45

b
 20

part

whole

9

b

45

100

part

whole

0% 45% 100%

0 9 b

Of the people at the bowling alley,

45% play for the bowling league. There are

a total of 9 bowling league players. How

many people are at the bowling alley?

To find how many people, the original

number or base, write and solve an

equation or a proportion.

45% of what numberis 9?

Let bequal the total number of people.

Write and solve an equation.

45% of b
 9

0.45b
 9

0.45b0.45
 9 0.45

b
 20

45% of 20 is 9.

So there are 20 people at the bowling alley.

Study these examples.

Divide both

sides by 0.45.

If Mike’s savings of $268.80 is 42% of

his savings goal, what amount of money

does Mike want to save?

42% of s
$268.80

0.42s
$268.80

s
$640

Mike wants to save $640.

$268.80

0.42

0.42s

0.42

Think

42% 
0.42

1.4

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