Gabriel and Lisbeth are having a discussion about rational and irrational numbers. Gabriel has been performing an experiment by measuring circles. He used a string and a ruler to measure the distance around several circles, as well as their diameters.

Gabriel records the distance and diameters in the table shown.

diameter (in.). distance (in.)

7____________22

3____________9.5

6.25_________19.75

8_____________25

2.5___________8

Then, after he plots the points on a graph, he draws a line of best fit. This is a straight line that most closely follows a trend in the data. He then calculates its slope.
y=3.1434x

Gabriel claims that the slope of the line, approximately 3.14, represents the irrational number ㅠ. Lisbeth is confused and asks how dividing two rational numbers can result in an irrational number. How can Gabriel respond to her question? He can think of two possible claims:

Claim A: Maybe is actually a rational number.

Claim B: Maybe the circumference is actually irrational.

Choose one claim that you think could be true and assume that the other is false. Write a script for what Gabriel could say to Lisbeth to explain why one could be possible and the other cannot.

If you are not sure how to proceed, here are some tips you can use as you

work through each Try This question:

1. For Claim A, Gabriel could explain what the criteria are for a number to be considered rational and describe how does or does not meet those criteria.

Refer to the section on sums and products of rational numbers for further details.

2. For Claim B, Gabriel could use the properties of multiplying rational and irrational numbers together to support or refute it. Refer to the section on sums and products of rational and irrational numbers for further details

3 answers

Gabriel's Response to Lisbeth:


Gabriel: "Hey Lisbeth, I understand your confusion about how dividing two rational numbers can result in an irrational number. Let me clarify things for you by discussing two claims. I’ll go with Claim B: Maybe the circumference is actually irrational."

Gabriel: "First, let’s think about Claim A. If we suppose that \( \pi \) is actually a rational number. A rational number is defined as any number that can be expressed as the fraction of two integers, \( \frac{a}{b} \), where \( b \) is not zero. However, \( \pi \) represents the ratio of the circumference of a circle to its diameter. It has been proven that \( \pi \) cannot be expressed as such a fraction; therefore, \( \pi \) is an irrational number."

Gabriel: "Now, let’s look at Claim B in detail. When I say, 'Maybe the circumference is actually irrational,' I mean that the distance around a circle (the circumference) is indeed based on our measurement of its diameter multiplied by \( \pi \). The formula for circumference is \( C = \pi \cdot d \) where \( d \) is the diameter.

Since \( \pi \) is irrational, and when we multiply it with a rational number (the diameter), the result remains irrational. This is a well-known property: the product of a rational number and an irrational number is always irrational."

Gabriel: "For the measurements we have, when I calculated the slopes, I was approximating \( \pi \) to about 3.14 based on the ratio of the circumference to the diameter from my measurements. While the slope I found gives a rational approximation, the actual value of \( \pi \) is irrational. This means that the circumference for any circle will inherently involve \( \pi \), keeping that irrational nature."

Gabriel: "So, in conclusion, Claim B holds true: The circumference of a circle is indeed irrational because it ultimately relies on the irrational number \( \pi \). This explains why our measurements reveal a slope that approximates \( \pi \) yet retains that characteristic of being irrational."

Gabriel: "In contrast, Claim A must be false because \( \pi \) being a rational number just doesn’t hold up against the definitions we have."

Gabriel: "Does that clear things up for you, Lisbeth?"


This dialogue effectively explains why Claim B could be true while asserting that Claim A cannot be, thus addressing Lisbeth's confusion about rational and irrational numbers.

Hey bot, thank you so much, but could you please make it little bit shorter

Sure! Here’s a more concise version of Gabriel's response:


Gabriel: "Hey Lisbeth, I understand your confusion. Let's discuss two claims. I believe Claim B is true: the circumference is actually irrational."

Gabriel: "First, if we consider Claim A and say \( \pi \) might be rational, that can't be true. A rational number can be expressed as a fraction of two integers, but \( \pi \) cannot be. It's been proven to be irrational."

Gabriel: "Now, with Claim B: The formula for the circumference of a circle is \( C = \pi \cdot d \) (where \( d \) is the diameter). Since \( \pi \) is irrational, any result from multiplying it by a rational number (the diameter) will also be irrational."

Gabriel: "So, while my slope approximates \( \pi \) as about 3.14, the actual value remains irrational. This is why the circumference is considered irrational too."

Gabriel: "To sum up, Claim B is true because the circumference involves \( \pi \), and Claim A is false. Does that help clarify things?"


This version maintains the key points while being more succinct.