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Express each of the following approximations of \(\pi\) to six significant figures: (a) \(22 / 7,\) (b) \(355 / 113 .\) (c) Are these approximations accurate to that precision?

Short Answer

Expert verified
(a) 3.14286, (b) 3.14159. Only (b) is accurate to six significant figures.

Step by step solution

01

Calculate the value of 22/7

Divide 22 by 7 to find the first approximation of \(\pi\). Use a calculator to find: \(\frac{22}{7} = 3.142857142857...\).
02

Round 22/7 to Six Significant Figures

Round the result from Step 1 to six significant figures. \(3.142857142857...\) rounds to \(3.14286\) for the first approximation.
03

Calculate the value of 355/113

Divide 355 by 113 to find the second approximation of \(\pi\). Use a calculator to find: \(\frac{355}{113} = 3.14159292035398...\).
04

Round 355/113 to Six Significant Figures

Round the result from Step 3 to six significant figures. \(3.14159292035398...\) rounds to \(3.14159\) for the second approximation.
05

Determine Accuracy to Six Significant Figures

Compare each approximation to the actual value of \(\pi\), which is \(3.14159265358979...\). The approximation \(3.14159\) from \(355/113\) matches the first six digits of \(\pi\), making it accurate to six significant figures. The approximation \(3.14286\) from \(22/7\) does not match the digits of \(\pi\), and so it is not accurate to six significant figures.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Approximations of Pi
Approximations of \(\pi\) have fascinated mathematicians for centuries. \(\pi\) itself, the ratio of a circle's circumference to its diameter, is an irrational number. This means its decimal form never ends and does not repeat. Since \(\pi\) is not a simple fraction, we often use rational approximations to work with it easily. Some of the commonly used approximations of \(\pi\) are \(\frac{22}{7}\) and \(\frac{355}{113}\). These fractions have been chosen because they offer close values to true \(\pi\).
* \(\frac{22}{7}\) approximates \(\pi\) as \(3.142857...\), often used for its simplicity.
* \(\frac{355}{113}\) is a more precise approximation, yielding a value of \(3.14159292035398...\).
Both serve as useful tools in calculations, making seemingly complex math problems simpler to solve.
Accuracy in Mathematics
Accuracy in mathematics is about how close an estimated value is to the true value. When working with numbers, especially approximations, it's crucial to understand how accurate they are. The precision can greatly affect the outcome of calculations. In the context of \(\pi\), an accurate approximation is one that closely matches the first several digits of the true \(\pi\) value \(3.14159265358979...\). Each digit in these numbers represents a level of precision, or accuracy, we aim to achieve.
For instance, we see that \(\frac{355}{113}\) provides a highly accurate result coinciding with the first six digits of \(\pi\). In contrast, \(\frac{22}{7}\) diverges after relatively few digits. It's essential to choose the right approximation depending on the level of precision required for a mathematical problem.
Rational Approximations
Rational approximations are fractions that closely represent irrational numbers like \(\pi\). These approximations simplify complex calculations by providing a number that's close enough to the actual value.A rational number is any number that can be represented as the quotient of two integers. \(\frac{22}{7}\) and \(\frac{355}{113}\) are clear examples where rational numbers are used to approximate irrational numbers.
* \(\frac{22}{7}\) is widely known though not the most accurate, yet it is easy to remember and use.
* \(\frac{355}{113}\) offers a much closer approximation to \(\pi\). It was discovered by the Chinese mathematician Zu Chongzhi and remains popular for precise calculations.
Understanding these approximations allows us to perform mathematical operations with reasonable precision without delving into infinite non-repeating decimals of irrational numbers. It’s like having a practical shorthand for an otherwise complex value.
Rounding Numbers
Rounding numbers is a mathematical technique used to simplify numbers while retaining their approximate value. When rounding, you decide how many digits are needed, usually depending on the required precision for a task. Significant figures are used to indicate the precision of a number. When dealing with approximations of \(\pi\), like \(\frac{22}{7}\) or \(\frac{355}{113}\), we round the unending decimals to a manageable number of significant figures. * \(\frac{22}{7}\) is rounded to six significant figures as \(3.14286\).
* \(\frac{355}{113}\) is rounded more precisely to \(3.14159\), aligning closely with \(\pi\).Using significant figures ensures you maintain the essential accuracy without unnecessary complexity. This practice is invaluable in scientific calculations where precision is crucial but ease of use is also necessary. Rounding helps to communicate and work with numbers more effectively in real-world situations.

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Most popular questions from this chapter

Some commonly occurring quantities. All of the quantities that follow will occur frequently in your study of physics. (a) Express the speed of light \(\left(3.00 \times 10^{8} \mathrm{~m} / \mathrm{s}\right)\) in \(\mathrm{mi} / \mathrm{s}\) and \(\mathrm{mi} / \mathrm{h} .\) (b) Find the speed of sound in air at \(0^{\circ} \mathrm{C}(1100 \mathrm{ft} / \mathrm{s})\) in \(\mathrm{m} / \mathrm{s}\) and \(\mathrm{mi} / \mathrm{h} .\) (c) Show that \(60 \mathrm{mi} / \mathrm{h}\) is the same as \(88 \mathrm{ft} / \mathrm{s}\). (d) Convert the acceleration of a freely falling body \(\left(9.8 \mathrm{~m} / \mathrm{s}^{2}\right)\) to \(\mathrm{ft} / \mathrm{s}^{2}\).

(a) How many ohms are there in a 7.85 megohm resistor? (b) Typical laboratory capacitors are around 5 picofarads. How many farads are they? (c) The speed of light in vacuum is \(3.00 \times 10^{8} \mathrm{~m} / \mathrm{s}\) Express this speed in gigameters per second. (d) The wavelength of visible light is between \(400 \mathrm{nm}\) and \(700 \mathrm{nm}\). Express this wavelength in meters. (e) The diameter of a typical atomic nucleus is about 2 femtometers. Express this diameter in meters.

You are designing a space station and want to get some idea about how large it should be to provide adequate air for the astronauts. Normally, the air is replenished, but for security, you decide that there should be enough to last for 2 weeks in case of a malfunction. (a) Estimate how many cubic meters of air an average person breathes in 2 weeks. A typical human breathes about \(1 / 2 \mathrm{~L}\) per breath. (b) If the space station is to be spherical, what should be its diameter to contain all the air you calculated in part (a)?

In each of the cases that follow, the components of a vector \(A\) are given. Find the magnitude of that vector and the counterclockwise angle it makes with the \(+x\) axis. Also, sketch each vector approximately to scale to see if your calculated answers seem reasonable. (a) \(A_{x}=4.0 \mathrm{~m}, A_{y}=5.0 \mathrm{~m}\) (b) \(A_{x}=-3.0 \mathrm{~km}, A_{y}=-6.0 \mathrm{~km}\) (c) \(A_{x}=9.0 \mathrm{~m} / \mathrm{s}, A_{y}=-17 \mathrm{~m} / \mathrm{s}\) (d) \(A_{x}=-8.0 \mathrm{~N}, A_{y}=12 \mathrm{~N}\)

On a single diagram, carefully sketch each force vector to scale and identify its magnitude and direction on your drawing: (a) \(60 \mathrm{lb}\) at \(25^{\circ}\) east of north, (b) \(40 \mathrm{lb}\) at \(\pi / 3\) south of west, (c) \(100 \mathrm{lb}\) at \(40^{\circ}\) north of west, (d) \(50 \mathrm{lb}\) at \(\pi / 6\) east of south.

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