Q:

Different sizes of ribbon need to be cut to go around various shapes. All of the following sizes are in inches. π , √5 ,√8 ,2√5 (a)Without using your calculator, approximate the decimal equivalent of each number to the nearest tenth. (b)Order the ribbon sizes from least to greatest. Use the original numbers given.

Accepted Solution

A:
(a) To approximate [tex] \pi [/tex], we are going to use a compass to draw a cirle of radius 2 and circumference 12.5. Remember that [tex] \pi [/tex] is the ratio between the circumference of a circle and its diameter; since the diameter of a circle is two times its radius, we can find [tex] \pi [/tex] using the equation: [tex] \pi = \frac{cricunference}{2*radius} [/tex]
[tex] \pi = \frac{12.5}{2(2)} [/tex]
[tex] \pi = \frac{12.5}{4} [/tex]
[tex] \pi =3.125[/tex] 
And to the nearest tenth:
[tex] \pi =3.1[/tex]

To approximate [tex] \sqrt{2} [/tex], we are going to use the Babylonian method:
Step 1. We are going to make a guess. Our guess is 2 because [tex] \sqrt{4} =2[/tex], so [tex] \sqrt{5} [/tex] must be close to 2.
Step 2. We are going to divide 5 by 2: 
[tex] \frac{5}{2} =2.5[/tex]
Step 3.  We are going to find the average between our initial guest and the result of our previous calculation:
[tex] \frac{2+2.5}{2} = \frac{4.5}{2} =2.25[/tex]
And to the nearest tenth: [tex] \sqrt{5} =2.2[/tex]

To approximate [tex] \sqrt{8} [/tex], we are going to use the Babylonian method one more time:
Step 1. Our guess is 3 because [tex] \sqrt{9} =3[/tex], so [tex] \sqrt{8} [/tex] must be close to 3.
Step 2. We are going to divide 8 by 3:
[tex] \frac{8}{3} =2.6[/tex]
Step 3.  We are going to find the average between our initial guest and the result of our previous calculation:
[tex] \frac{3+2.6}{2} = \frac{5.6}{2} =2.8[/tex]
[tex] \sqrt{8} =2.8[/tex]

To approximate [tex]2 \sqrt{5} [/tex] we are going to multiply our approximation of [tex] \sqrt{5} [/tex] and multiply it by 2:
[tex]2 \sqrt{5} =2*2.2[/tex]
[tex]2 \sqrt{5}=4.4[/tex]

(b) Since we have our irrational numbers expressed as decimal approximations, we can compare them to arrange them form least to greatest:
2.2,2.8,3.1,4.4
Now, we just need to replace the decimal approximations with the original numbers:
[tex] \sqrt{5} [/tex],[tex] \sqrt{8} [/tex],[tex] \pi [/tex],[tex]2 \sqrt{5} [/tex]

We can conclude that ordering the ribbon sizes from least to greatest we get:
[tex] \sqrt{5} [/tex],[tex] \sqrt{8} [/tex],[tex] \pi [/tex],[tex]2 \sqrt{5} [/tex]