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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.

User Webster
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1 Answer

3 votes
(a) To approximate
\pi, we are going to use a compass to draw a cirle of radius 2 and circumference 12.5. Remember that
\pi 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
\pi using the equation:
\pi = (cricunference)/(2*radius)

\pi = (12.5)/(2(2))

\pi = (12.5)/(4)

\pi =3.125
And to the nearest tenth:

\pi =3.1

To approximate
√(2), we are going to use the Babylonian method:
Step 1. We are going to make a guess. Our guess is 2 because
√(4) =2, so
√(5) must be close to 2.
Step 2. We are going to divide 5 by 2:

(5)/(2) =2.5
Step 3. We are going to find the average between our initial guest and the result of our previous calculation:

(2+2.5)/(2) = (4.5)/(2) =2.25
And to the nearest tenth:
√(5) =2.2

To approximate
√(8), we are going to use the Babylonian method one more time:
Step 1. Our guess is 3 because
√(9) =3, so
√(8) must be close to 3.
Step 2. We are going to divide 8 by 3:

(8)/(3) =2.6
Step 3. We are going to find the average between our initial guest and the result of our previous calculation:

(3+2.6)/(2) = (5.6)/(2) =2.8

√(8) =2.8

To approximate
2 √(5) we are going to multiply our approximation of
√(5) and multiply it by 2:

2 √(5) =2*2.2

2 √(5)=4.4

(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:

√(5),
√(8),
\pi,
2 √(5)

We can conclude that ordering the ribbon sizes from least to greatest we get:

√(5),
√(8),
\pi,
2 √(5)
Different sizes of ribbon need to be cut to go around various shapes. All of the following-example-1
User Szymon Roziewski
by
6.4k points
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