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love history [14]
4 years ago
6

A cell phone company says that a fully charged battery lasts 14 hours. In reality, each battery behaves a little differently. Fo

r a large quantity of fully charged batteries, the mean length of time that batteries last is 14 hours, with a standard deviation of 1 hour. Assume that the lengths of time that battery charges last can be modeled by a normal distribution.
What percent of fully charged cell phone batteries would be expected to last longer than 14 hours?
Mathematics
1 answer:
gregori [183]4 years ago
8 0

Answer:

The percentage is 50%

Step-by-step explanation:

From the question we are told that  

     The  mean is  \mu  =  14 \  hours

     The  standard deviation is \sigma =  1 \  hour

Generally on the normal distribution curve the mean divides the curve into  two. with the half to the left of the mean (50% to the left )representing the percentage of the batteries that will last less than 14 hours and  the area under the curve to the right (50% to the right)representing the percentage of batteries that will last longer than mean (14 hours )

Hence the percentage of the cell phone batteries that will be expected to last longer than 14 hours is 50%

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A rocket is launched from a tower what time will the rocket reach its max
Lena [83]

Answer:

Step-by-step explanation:

A science class designed a ball launcher and tested it by shooting a tennis ball up and off the top of a 15-story building. They determined that the motion of the ball could be described by the function: h(t) = -16t2 + 144t + 160, where ‘t’ represents the time the ball is in the air in seconds and h(t) represents the height, in feet, of the ball above the ground at time t.

a) Graph the function h(t) = -16t2 + 144t + 160 (see below)

      b) What is the height of the building?

The height of the building is also the height of the tennis ball before it is launched into the air. This occurs when t=0 so substitute 0 for t and you get:

H(0) = -16(0)2 + 144(0) + 160

The height of the building is 160 feet.

 c) At what time did the ball hit the ground?

The ball hits the ground when the height is 0. Therefore, we are looking for a solution to: -16t2 + 144t + 160 = 0

Use the quadratic formula or put this into a calculator. The solution is t=10 and -1, but only 10 makes sense. Therefore, the ball hits the ground at 10 seconds.

  d) At what time did the ball reach its maximum height?

You can put this into the calculator or you can realize that the maximum height is also

− the vertex. The x-value (‘t’ in this case) is 2

−144

which is (2)(−16) = 4.5.

Therefore, the ball reached its maximum height at 4.5 seconds.

   e) What is the maximum height of the ball?

We calculated the time of the maximum height (4.5 seconds). Therefore, substitute 4.5 into the function to find the maximum height.

-16(4.5)2 + 144(4.5) + 160

The maximum height is 484 feet.

5 0
3 years ago
What is the volume of a hemisphere with a radius of 34.1 in, rounded to the nearest tenth of a cubic inch?
White raven [17]

Answer:83046.6

Step-by-step explanation:

4 0
3 years ago
Lucy has 4 more than 1/3 the number of pairs of socks as her sister. Lucy has at most 9 pairs of socks. How many pairs of socks
Volgvan

Answer: at most 15 pairs of socks

Step-by-step explanation:

Let the number of pair of socks of her sister be x , and let the number of pairs Lucy has be y.

Since , Lucy has 4 more than 1/3 the number of pairs of socks as her sister, this means that

\frac{1}{3}x + 4 = y    .............................. equation 1

Also ,  Lucy has at most 9 pairs of socks , this means that

y\leq 9 ....................................... equation 2

Equating the two equations , we have

\frac{1}{3}x + 4 \leq 9

multiply through by 3

x + 12\leq 27

subtract 12 from both sides

x\leq 15

Therefore , the sister has at most 15 pairs of socks

4 0
3 years ago
30 in.<br> 20 in.<br> 36 in.<br> Find the area of the trapezoid shown above.<br> [?] square inches
Novay_Z [31]

Answer:

660 in^2

Step-by-step explanation:

The formula to calculate area of trapezoid : (a+b)/2*h (a: base, b: base, h: height)

(30+36)/2*20 = 660 in^2

3 0
3 years ago
Each of the four sides of a swimmimg pool measures 9 meters. The pool is 5 meters deep. How much water will be needed to fill it
netineya [11]
In this problem, we are asked for the volume of the pool filled with water. In this case, the volume of the rectangular prism is equal to length times width times height. Since length and width are equal, the formula includes the squaring of the length. after substitution, the formula is 9^2 * 5 equal to 405 m3. 
5 0
4 years ago
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