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iris [78.8K]
3 years ago
14

Merta reports that 74% of its trains are on time. A check of 60 randomly selected trains shows that 38 of them arrived on time.

Find the probability that among the 60 trains, 38 or fewer arrive on time. Based on the result, does it seem plausible that the "on-time" rate of 74% could be correct?
Mathematics
1 answer:
kenny6666 [7]3 years ago
6 0

Answer:

No, the on-time rate of 74% is not correct.

Solution:

As per the question:

Sample size, n = 60

The proportion of the population, P' = 74% = 0.74

q' = 1 - 0.74 = 0.26

We need to find the probability that out of 60 trains, 38 or lesser trains arrive on time.

Now,

The proportion of the given sample, p = \frac{38}{60} = 0.634

Therefore, the probability is given by:

P(p\leq 0.634) = [\frac{p - P'}{\sqrt{\frac{P'q'}{n}}}]\leq [\frac{0.634 - 0.74}{\sqrt{\frac{0.74\times 0.26}{60}}}]

P(p\leq 0.634) = P[z\leq -1.87188]

P(p\leq 0.634) = P[z\leq -1.87] = 0.0298

Therefore, Probability of the 38 or lesser trains out of 60 trains to be on time is 0.0298 or 2.98 %

Thus the on-time rate of 74% is incorrect.

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Find the dimensions of the open rectangular box of maximum volume that can be made from a sheet of cardboard 23 in. by 13 in. by
faltersainse [42]

Answer:

The dimension of the box is 17.66 in by 7.66 in by 2.67 in.

Therefore the volume of the box is 361.19 in^3.

Step-by-step explanation:

Given that the dimensions of a cardboard is 23 in by 13 in.

Let the side of the square be x in.

Then the length of the box= (23-2x) in

and the width of the box =(13-2x) in

and height = x in.

The volume of the box is = length ×width × height

                                         =[(23-2x)(13-2x)x] in^3

                                         =(299x-72x² +4x^3) in^3

∴V=299x-72x² +4x³

Differentiating with respect x

V'= 299-144x+12x²

Again differentiating with respect x

V''= -144+24x

To find the dimensions, we set V'=0

∴299-144x+12x²=0

Applying Sridharacharya formula that is the solution of a quadratic equation ax²+bx+c is x=\frac{-b\pm\sqrt{b^2-4ac}}{2a}

Here a=12, b=-144 , c=299

\therefore x=\frac{-(-144)\pm\sqrt{(-144)^2-4.12.299}}{2.12}

\Rightarrow x= 9.33, 2.67

If  we take x=9.33 in, then the width of the box [13-(2×9.33)] will negative.

∴x = 2.67 in

If at x = 2.67, V''<0 , then the volume of the box will be maximum or V''>0 then volume of the box will be minimum.

V''|_{x=2.67}=-144+(24\times 2.67)=-79.92

Therefore  at x = 2.67, the volume of the box maximum.

The length of the box =[23-(2×2.67)] in

                                    =17.66 in

The width of the box =[13-(2×2.67)] in

                                  =7.66 in

The height of the box= 2.67 in

The dimension of the box is 17.66 in by 7.66 in by 2.67 in.

Therefore the volume of the box is =(17.66×7.66×2.67) in^3

                                                            =361.19 in^3

8 0
3 years ago
Andre took 6 kicks and made 4 goals: 4 out of six. Tom wants to take more than 20 kicks and make a equivalent fraction to Andre.
Zanzabum

Answer:

Tom can either take 24 kicks and make 16 goals or 30 kicks and make 20 goals.

Step-by-step explanation:

Andre made 4 goals out of 6 kicks.

Tom wants to take more than 20 kicks and to make an equivalent fraction to Andre.

<u>Possibility 1:</u>

Let Tom makes 24 kicks.

To get 24, we need to multiply the denominator of Andre's fraction by 4.

So, \frac{4}{6} =\frac{16}{24}

Therefore, Tom can take 24 kicks and make 16 goals.


<u>Possibility 2:</u>

Let Tom makes 30 kicks.

To get 30, we need to multiply the denominator of Andre's fraction by 5.

So, \frac{4}{6} =\frac{20}{30}

Therefore, Tom can take 30 kicks and make 20 goals.



8 0
3 years ago
What is -5/6 ÷ 9 /10 ?
vredina [299]
D: -25/27
-5/6  ÷  9/10  =  5/6  x   10/9   *when diving fractions, use recipricals.*
-5/6  ÷  10/9  =  - 25/27  *just multiply each numerator and denominator*
8 0
3 years ago
How does soil begin to form?
Nonamiya [84]

Answer:  Rock particles clump together in aggregate

Step-by-step explanation:

Soil minerals form the basis of soil. They are produced from rocks (parent material) through the processes of weathering and natural erosion. Water, wind, temperature change, gravity, chemical interaction, living organisms and pressure differences all help break down parent material.

3 0
3 years ago
1. is he equation true , false, or open
RideAnS [48]

Question 1:

For this case we have the following equation:

 5x ^ 2 = 6x + 11

We observe that the equation is a polynomial of the second degree.

Therefore, the equation has two possible solutions.

The variable of the equation for this case is x.

In this case, we have an open equation because we have a variable.

Rewriting the equation we have:

5x ^ 2 - 6x - 11 = 0

Answer:

open, there is a variable.


Question 2:

For this case we have the following equation:

 2-8x = -6

From here, we must clear the value of x.

For this, we follow the following steps:

1) Pass the value of 8x adding:

2 = -6 + 8x

2) Pass the value of 6 adding:

2 + 6 = 8x

3) Add the values ​​on the same side of equality:

 8x = 8

4) Pass the 8 to divide:

x = \frac{8}{8} = 1

Answer:

The value of x is given by:

x = 1


Question 3:

For this case we have the following equation:

 y = x-4

The ordered pair solution is the one that satisfies both sides of the equation.

For the point (6, 2) we have:

x = 6  y = 2

Substituting values ​​we have:

2 = 6-4  2 = 2

We observe that both sides of the equation are equal.

Therefore, the ordered pair solution is (6, 2)

Answer:

An ordered pair that is a solution of the equation y = x-4 is:

(6, 2)

3 0
3 years ago
Read 2 more answers
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