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il63 [147K]
3 years ago
13

Lin runs 5 laps around a track in 6 minutes If Lin runs 21 laps at the same rate, how long does it take her

Mathematics
1 answer:
nydimaria [60]3 years ago
4 0

Answer:

It would take her 25.2 minutes

Step-by-step explanation:

6 divided by 5 gives you the 1.2 minutes

Then I would do 1.2 minutes for each lap  * 21 laps = 25.2 minutes

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A factory dumps an average of 2.43 tons of pollutants into a river every week. if the standard deviation is 0.88 tons, what is t
vovikov84 [41]
25.8%  
First, determine how many standard deviations from the norm that 3 tons are. So:
 (3 - 2.43) / 0.88 = 0.57/0.88 = 0.647727273  
So 3 tons would be 0.647727273 deviations from the norm. Now using a standard normal table, lookup the value 0.65 (the table I'm using has z-values to only 2 decimal places, so I rounded the z-value I got from 0.647727273 to 0.65). The value I got is 0.24215. Now this value is the probability of getting a value between the mean and the z-score. What I want is the probability of getting that z-score and anything higher. So subtract the value from 0.5, so 0.5 - 0.24215 = 0.25785 = 25.785%  
So the probability that more than 3 tons will be dumped in a week is 25.8%
5 0
3 years ago
Which of the following is equal to the rational expression when x 2 or -4? 5(x-2)/(x-2)(x+4)
Elena L [17]
Wait when x= 2 or -4? is the second part options or 5(x-2)/(x-2)(x+4)
6 0
3 years ago
Solve:<br><br> (15/x)+(9x-7)/(x+2)=9
hram777 [196]

Answer:x=3

Step-by-step explanation:

D( x )

x+2 = 0

x = 0

x+2 = 0

x+2 = 0

x+2 = 0 // - 2

x = -2

x = 0

x = 0

x in (-oo:-2) U (-2:0) U (0:+oo)

(9*x-7)/(x+2)+15/x = 9 // - 9

(9*x-7)/(x+2)+15/x-9 = 0

(x*(9*x-7))/(x*(x+2))+(15*(x+2))/(x*(x+2))+(-9*x*(x+2))/(x*(x+2)) = 0

x*(9*x-7)+15*(x+2)-9*x*(x+2) = 0

9*x^2-9*x^2+8*x-18*x+30 = 0

30-10*x = 0

(30-10*x)/(x*(x+2)) = 0

(30-10*x)/(x*(x+2)) = 0 // * x*(x+2)

30-10*x = 0

30-10*x = 0 // - 30

-10*x = -30 // : -10

x = -30/(-10)

x = 3

x = 3

3 0
3 years ago
A food company sells salmon to various customers. The mean weight of the salmon is 37 lb with a standard deviation of 2 lbs. The
brilliants [131]

Answer:

The standard deviation for the mean weigth of Salmon is 2/3 lbs for restaurants, 2/7 lbs for grocery stores and 1/4 lbs for discount order stores.

Step-by-step explanation:

The mean sample of the sum of n random variables is

\overline{X} = \frac{X_1+X_2+...+X_n}{n}

If X_1, ..., X_n are indentically distributed and independent, like in the situation of the problem, then the variance of X_1 + .... + X_n will be the sum of the variances, in other words, it will be n times the variance of X_1 .

However if we multiply this mean by 1/n (in other words, divide by n), then we have to divide the variance by 1/n², thus \overkine{X} = \frac{V(X_1)}{n} and as a result, the standard deviation of \overline{X} is the standard deviation of X_1 divided by \sqrt{n} .

Since the standard deviation of the weigth of a Salmon is 2 lbs, then the standard deviations for the mean weigth will be:

  • Restaurants: We have boxes with 9 salmon each, so it will be \frac{2}{\sqrt{9}} = \frac{2}{3}
  • Grocery stores: Each carton has 49 salmon, thus the standard deviation is \frac{2}{\sqrt{49}} = \frac{2}{7}
  • Discount outlet stores: Each pallet has 64 salmon, as a result, the standard deviation is \frac{2}{\sqrt{64}} = \frac{1}{4}

We conclude that de standard deivation of the mean weigth of salmon of the types of shipment given is: 2/3 lbs for restaurants, 2/7 lbs for grocery stores and 1/4 lbs for discount outlet stores.

7 0
3 years ago
a rectangle has an area of x2+8x+15 square meters and a width of x+3 what expression represents the length of the rectangle
anzhelika [568]

Answer:

1x + 5

Step-by-step explanation:

Since the area of a rectangle of width w and length l is A = l*w,

length = Area / Width.

Here,                             x^2 + 8x + 15

length of rectangle  = ----------------------

                                            x + 3

Use synthetic division to perform the above.  The coefficients of the quadratic are a = 1, b = 8 and c = 15, and the divisor is -3 (from (x + 3).

-3      /  1        8        15

                    -3        -15

        -------------------------

            1         5        0

Since the remainer is zero (0), -3 is a root and 1x + 5 is a factor of the quadratic.  This factor, representing the length of the rectangle, is 1x + 5.

Next time, kindly share the answer choices.  Thank you.

6 0
3 years ago
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