Answer:
B
Step-by-step explanation:
I Had this
Hello!
10 seconds to return to the ground.
7 seconds to reach 576 feet above the ground.
Find the amount of time taken to reach the ground by setting the equation equal to 0:
0 = -16t² + 80t + 800
Factor out -16 from the equation:
0 = -16(t² - 5t - 50)
Factor the terms inside of the parenthesis:
0 = -16(t - 10)(t + 5)
Find the zeros:
t - 10 = 0
t = 10
t + 5 = 0
t = -5
Time can only be positive in this instance, so the correct answer is 10 sec.
Find the time by substituting in 576 for the height:
576 = -16t² + 80t + 800
Subtract 800 from both sides:
-224 = -16t² + 80t
Rearrange:
0 = -16t² + 80t + 224
Simplify:
0 = -16(t² - 5t - 14)
0 = -16(t - 7)(t + 2)
t = 7 seconds.
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Mean diameter = 25 mm
Standard deviation = 0.2 mm
25.6 mm - 25 mm = 0.6 mm
0.6 mm : 0.2 mm = 3
Answer:
A ball bearing with a diameter 25.6 mm differs from the mean
D ) 3 standard deviations.
In case you don't know your times-3 numbers well enough to recognize the answer right away, you can check the second data point.
.. a. 2^3 = 8 ≠ 6
.. b. 3^2 = 9 ≠ 6
.. c. 3*2 = 6
.. d. 2 +3 = 5 ≠ 6
Only selection C makes sense.
