Year 9 Interactive Maths - Second Edition

Dividing a Quantity in a Given Ratio

That is, AP = 3 cm and BP = 6 cm.

Conversely, if we know that the point P divides the line segment AB of length 9 cm in the ratio
1 : 2, we can determine the lengths of AP and BP as follows:

So, the lengths of AP and BP are 3 cm and 6 cm, respectively.

Check:

3 cm + 6 cm = 9 cm

Example 3

Anne and Allen worked together on a project and received $250 for their completed work. Allen worked for 2 days and Anne worked for 3 days, and they agree to divide the money between them in the ratio 2 : 3.  How much should each receive?

Solution:

We picture the $250 divided into equal parts.

Now, there are 5 parts and the smaller amount is 2 of them.

So, the smaller amount (Allen's share) is $100, and so Anne's share is $250 – $100 = $150.

Example 4

An urn contains red and black marbles in the ratio 2 : 3.  If there are 40 red marbles, find the total number of marbles in the urn.

Solution:

Ratio of red marbles to black marbles = 2 : 3

Number of red marbles (2 parts out of 5) = 40

Let x be the number of marbles in the urn.

Hence the number of marbles in the urn is 100.