Number And Algebra - Chapter 7 Applying Ratios And Rates - Nelson Think Math Page 15
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Applying ratios and rates
Example
14
Which is the larger ratio, 3 : 7 or 5 : 12?
Solution
Change 3 : 7 to the form . . . : 1.
3 : 7
¼ 3 4 7 : 7 4 7 0.429 : 1
Change 5 : 12 to the form . . . : 1.
5 : 12
¼ 5 4 12 : 12 4 12 0.417 : 1
Compare the ratio values.
0.429 > 0.417
Write the answer.
3 : 7 is larger than 5 : 12.
Investigate: Newspaper ratios
Obtain copies of two different daily newspapers. Make
sure that they are for the same day of the week.
1 Compare the newspapers by doing the following
things.
• Find the number of pages in each paper.
• Measure the length and width of the pages of
each paper and calculate the area of one page for
each.
• Measure the length and width of the columns of
each paper and calculate the area of a column in
each paper.
2 Now use areas or columns to determine the space
each newspaper devotes to different features as follows. Compare the spaces by finding
the ratio of the feature to the total for each newspaper.
• Which newspaper uses more space for news headlines?
• Which newspaper uses more space for news?
• Which newspaper uses more space for cartoons?
• Which newspaper uses more space for advertisements?
• Which newspaper uses more space for sport?
3 Use your results to decide which is the better newspaper for a family.
Sometimes different quantities are related by the same ratios. For example, if you put more apples
in a bag, then the price goes up in the same ratio as the weight (number) of apples. Increasing the
speed of a conveyer belt decreases the time taken to transfer the same amount of material.
Problems of this nature can be done using equivalent ratios. Take care in putting them the right
way round!
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