# Proportional Problems

## Simple Proportion

If something is in proportion to something else, it means that there is a link between the two things. For example,
a ratio is in proportion as the two numbers are linked. Look at the example on the right to get started. There are
10 photos on one CD. The question is? How many photos are there on 4 CDs. To find the answer, we have to
multiply the photos on one CD (10) by 4 as there are four CDs. This then gives us 40. There are 40 photos an 4
CDs.
Solving Proportional Problems using the Unitary Method
The unitary method is a method in which we find the value for 1 unit (eg: the price of one bread, the weight of one camel, etc.) to solve more complicated
proportional problems. There are two examples underneath which explain how the unitary method is applied in different situations.
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Example 1
There are 240 bananas in 8 boxes. How many bananas are
there in one box?
8 boxes > 240 bananas
1 box > ? bananas
240÷8 = ? = 30
1 box > 30 bananas.
There are 30 bananas in one box.
We have found this solution b dividing the number of
bananas by the number of boxes. This is basically the
reverse of what we have done in the example above.

### 10 Photos

### 40 Photos

1 CD

4 CDs

Example 2
There are 84 people in 21 cars. How many people are there
in one car?
21 cars > 84 people
1 car > ? people
84÷21 = ? = 4
1 car > 4 people
There are 4 people in one car.
We have found this solution using the same method as in
the example above.

Example 1
There are 140 breads sold in 7 hours. How many breads are
sold in 9 hours?
7 hours > 140 breads
9 hours > ? breads
140÷7 = 20
1 hour > 20 breads
20×9 = 180
9 hours > 180 breads
180 breads are sold in 9 hours.
We have solved this problem by finding out how many
breads are sold in 1 hour and then multiplying this value by
9. This is the unitary method in action.

Example 2
A lift can transport 75 tourists in 3 rides. How many tourist
can be transported in 100 rides?
3 rides > 75 tourists
100 rides > ? tourists
75÷3 = 25
1 ride > 25 tourists
25×100 = 2500
100 rides > 2500 tourists
2500 tourists can be transported in 100 rides.
We have solved this problem using the unitary method (by
finding how many tourists are transported in 1 ride.) We
then multiplied this value by 100 to find how many were
transported in 100 rides.

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Chapter 9.2: Learning Outcomes
Students will be able to solve simple proportional problems!
Students will be able to find answers to proportional problems using the
unitary method!

## VIDEO LESSON:

## NOT CURRENTLY AVAILABLE!