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Answer:
61 commuters must be randomly selected to estimate the mean driving time of Chicago commuters.
Step-by-step explanation:
Given : We want 95% confidence that the sample mean is within 3 minutes of the population mean, and the population standard deviation is known to be 12 minutes.
To find : How many commuters must be randomly selected to estimate the mean driving time of Chicago commuters?
Solution :
At 95% confidence the z-value is z=1.96
The sample mean is within 3 minutes of the population mean i.e. margin of error is E=3 minutes
The population standard deviation is s=12 minutes
n is the number of sample
The formula of margin of error is given by,
Substitute the value in the formula,
Squaring both side,
Therefore, 61 commuters must be randomly selected to estimate the mean driving time of Chicago commuters.
The length of the shorter leg is 14 inches.
We will set up two equations for this; first, for the perimeter. We will call the legs a and b:
a + b + 50 = 112
Subtract 50 from both sides:
a + b + 50 - 50 = 112 - 50
a + b = 62
We will isolate a, so we can use substitution. Subtract b from both sides:
a + b - b = 62 - b
a = 62 - b
Now we will set up our Pythagorean theorem equation:
a² + b² = 50²
a² + b² = 2500
We will substitute our value for a from the first equation into this one:
(62-b)² + b² = 2500
(62 - b)(62 - b) + b² = 2500
Multiplying the binomials, we have:
62*62 - b*62 - b*62 -b(-b) + b² = 2500
3844 - 62b - 62b + b² + b² = 2500
Combining like terms:
3844 - 124b + 2b² = 2500
To set it equal to 0 and solve, we subtract 2500 from both sides:
3844 - 124b + 2b² - 2500 = 2500 - 2500
1344 - 124b + 2b² = 0
In standard form, we have
2b² - 124b + 1344 = 0
Using the quadratic formula,
The shorter leg is 14 and the longer one is 48.
We will set up two equations for this; first, for the perimeter. We will call the legs a and b:
a + b + 50 = 112
Subtract 50 from both sides:
a + b + 50 - 50 = 112 - 50
a + b = 62
We will isolate a, so we can use substitution. Subtract b from both sides:
a + b - b = 62 - b
a = 62 - b
Now we will set up our Pythagorean theorem equation:
a² + b² = 50²
a² + b² = 2500
We will substitute our value for a from the first equation into this one:
(62-b)² + b² = 2500
(62 - b)(62 - b) + b² = 2500
Multiplying the binomials, we have:
62*62 - b*62 - b*62 -b(-b) + b² = 2500
3844 - 62b - 62b + b² + b² = 2500
Combining like terms:
3844 - 124b + 2b² = 2500
To set it equal to 0 and solve, we subtract 2500 from both sides:
3844 - 124b + 2b² - 2500 = 2500 - 2500
1344 - 124b + 2b² = 0
In standard form, we have
2b² - 124b + 1344 = 0
Using the quadratic formula,
The shorter leg is 14 and the longer one is 48.