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Comparing Ratios Using Tables & Graphs

Instructor: Lynne Hampson

Lynne Hampson has a Masters in Instr. Design & Bach. in Elem./Spec. Educ. She taught 8 years in Elem. Core, Science, Coding, Microsoft, Internet Safety, and Life Skills.

In this lesson, we will be creating ratio tables to help in making decisions regarding many life circumstances, such as calculating how much money you will earn in a certain number of hours. Using a table to show ratios will produce clues to an outcome that are based upon mathematical evidence.

Comparing Ratios Using Tables & Graphs Vocabulary

Ratios: A comparison of two or more values of objects.

Ratio Table: A box with columns and rows that will show trends in relation to the value of ratios increasing or decreasing. Ratio tables help us to solve real-world questions about the increase or decrease in needs, worth, size, etc.

Using a Ratio Table

The ratio table could be long, or it could be short. It all depends on what information is needed.

Let's say there was a party, and the host was pretty sure there would be 10 people there. The host read a website that said for each 10 people, you will need 20 lbs. (pounds) of turkey.

Then, the host started getting phone calls from friends who just so happened to be driving into town the same time as his party. They said they might stop by for dinner. 'Eek, how much turkey should I buy now?', asked the host.

After that, he got another phone call about some family members who came down with the flu, and could not come to the party. 'Oh dear, now how many guests should I plan for?', he thought.

Then, he had a brain storm idea. He decided to sit down and work out a ratio table to make a final decision.

Remember the information about the turkey servings from above? It's time to put those numbers into action. If there were 10 guests, then 20 lbs. of turkey would be needed. (10:20 ratio)

The table started out like this:

helpmefixthis1

Then, he thought, 'What if I had 15 people come to my party?' So, he wrote 15 down as a possible scenario, under 'Number of People'. You can see the example below, but how did he come up with 30 lbs. of turkey on the other side?

ratiotables1

  • This problem involves an algebraic problem such as this: 10 x = 20.
  • Since division is the opposite of multiplication, we could also use division. 20 / 10 = _____.
  • Either way, you will come up with the same answer, 2.

Making a Rule

The rule is found by the beginning ratio, and then it is transferred to the other ratios. It is the information you begin with in the word problem. The rule here is: the number of people attending the party must be multiplied by 2 to find the amount of turkey they will need to eat at the party.

Now that you figured that out, go ahead and see how many pounds of turkey the guests will need if there were 20 people. Then, check your answer below:

ratiotables2

A ratio table can calculate how much to serve more people, and it also allows calculation for less people than intended.

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