Use Indirect Proportion in Table Form

In this activity, we will find indirect proportion when it is presented in table form.

 

 

Remember

Direct proportion is 

As one amount increases the other increases by the same rate!

 

Indirect (or inverse) proportion is

As one amount increases the other decreases by the same rate!

 

An example of indirect proportion would be if we take a journey in the car - as the miles go up, the petrol will go down!

 

 

Let's look at a typical question.

 

Example

y is indirectly proportional to x

Complete the table below:

 

 

Solution

We need to look at the table to see where we have both the x and the y values.

We can use these to find the rule.

 

We have x = 8 when y = 3

To find the multiplier, we can do 8 x 3 = 24

(The inverse process from direct proportion where we divided here)

This gives us: y = 24 ÷ x

 

We can now fill in the gaps:

When x = 2, then y = 24 ÷ 2 = 12

When x = 6, then y = 24 ÷ 6 = 4

 

 

Notice that as the x value goes up, the y value goes down!

 

Let's try some more of these!