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mote1985 [20]
3 years ago
14

A plane flies 720 miles with the wind in 3 hours. The return trip against the wind takes 4 hours. What is the speed of the wind

and the speed of the plane in still air?
Mathematics
1 answer:
Mandarinka [93]3 years ago
4 0
Let p and w represent the speed of the plane and the speed of the wind, respectively.
.. speed = distance/time
.. p +w = 720/3 = 240
.. p -w = 720/4 = 180

Add the two equations to eliminate w.
.. 2p = 420
.. p = 210
.. w = p -180 = 30

The speed of the wind is 30 mph.
The speed of the plane in still air is 210 mph.
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Question:

Suppose that the populations of the United States and China both increase by 12 million people in one year. What would be the relative change for each country? Answer to the nearest tenth of a percent (1 decimal place). Make sure that you fill in each answer area before checking "How Did I Do?".

If you assume that the U.S. population is about 300 million, an increase of 12 million would result in a relative change of Number %.

If you assume that China has about 1 billion people, an increase of 12 million would result in a relative change of Number %.

Answer:

The relative change of the United States and China is 4% and 1.2%, respectively.

Step-by-step explanation:

Given

Represent population with p. So, we have:

United States

\triangle p = 12\ million

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China

\triangle p = 12\ million

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Required

Determine the relative change for each country

Relative change, C is calculated as:

C = \frac{\triangle p}{p} * 100\%

For United States

C = \frac{12\ million}{300\ million} * 100\%

C = \frac{12}{300} * 100\%

C = \frac{12 * 100}{300}\%

C = \frac{1200}{300}\%

C = 4\%

For China

C = \frac{12\ million}{1\ billion} * 100\%

C = \frac{12}{1000} * 100\%

C = \frac{12* 100}{1000} \%

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C = 1.2\%

The relative change of the United States and China is 4% and 1.2%, respectively.

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