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NISA [10]
2 years ago
15

A scientist running an experiment starts with 100 bacteria cells. These bacteria double their population every 15 hours. Find ho

w long it takes for the bacteria cells to increase to 300. Use the formula , where is the original number of bacteria cells, is the number after t hours, and d is the time taken to double the number. It takes hours for the number of bacteria to increase to 300.
Mathematics
2 answers:
IRISSAK [1]2 years ago
8 0
<h2>Hello!</h2>

The answer is: 23.77 hours

<h2>Why?</h2>

Total(t)=Start*2^\frac{t}{15}

Where:

Total(t) is equal to the amount for a determined time (in hours)

<em>Start</em> is the original amount

<em>t </em>is the time in hours.

For example, it's known from the statement that the bacteria double their population every 15 hours, so it can be written like this:

Total(15)=100*2^\frac{15}{15}=100*2^{1}=100*2=200

To calculate how long it takes for the bacteria cells to increase to 300, we should do the following calculation:

300=100*2^{\frac{t}{15} } } \\\frac{300}{100}=2^{\frac{t}{15} } }\\log(3)=log(2^{\frac{t}{15} })\\\\\\log(3)=\frac{t}{15}*log2\\t=\frac{log(3)}{log(2)} *15=23.77

So, to know if we are right, let's replace 23.77 h in the equation:

Total(t)=100*2^\frac{23.77}{15}=299.94

and 299.94≅300

Have a nice day!

Rina8888 [55]2 years ago
3 0

Answer:

23.77

Step-by-step explanation:

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An automotive manufacturer wants to know the proportion of new car buyers who prefer foreign cars over domestic. In an earlier s
anyanavicka [17]

Answer:

1,496 new car buyers

Step-by-step explanation:

The sample size n in Simple Random Sampling is given by

\bf n=\frac{z^2p(1-p)}{e^2}

where  

z = 1.645 is the critical value for a 90% confidence level (*)

p= 0.33 is the population proportion.

e = 0.02 is the margin of error

so  

\bf n=\frac{(1.645)^20.33*0.67}{0.02^2}=1,495.76\approx 1,496

<em>(*)</em><em>This is a point z such that the area under the Normal curve N(0,1) inside the interval [-z, z] equals 90% = 0.9</em>

It can be obtained in Excel or OpenOffice Calc with

<em>NORMSINV(0.95)</em>

6 0
2 years ago
A group of 12 people want to go to a concert. They can travel in a small car that takes one driver and one passenger and two car
trapecia [35]

Answer: There are 60 ways that they can travel to the concert.

Step-by-step explanation:

Since we have given that

Number of people want to go to a concert = 12

Number of cars = 3

Number of drivers in the group = 5

So, using the "Fundamental theorem of counting":

We get that

5\times 4\times 3\\\\=60

Hence, there are 60 ways that they can travel to the concert.

7 0
2 years ago
Find the surface area of the triangular prism. A triangular prism. The base is a right triangle with base 1 foot, height 2 feet
mylen [45]

Answer:

<h2>17.6ft²</h2>

Step-by-step explanation:

The formula for calculating the surface area of a triangular prism is expressed as shown below:

SA= bh + pH

b= base of the triangle

h- height of the triangle

p= perimeter of the triangle

H= height of the prism

Given b = 1foot

h = 2feet

perimeter of the triangle = sum of all its sides = 1ft + 2ft + 2.2ft

p = 5.2ft

H = 3ft

Substituting the values into the formula for finding the surface area:

SA = 1(2)+5.2(3)

SA = 2+15.6

SA = 17.6ft²

The surface area of the triangular prism is  17.6ft²

3 0
2 years ago
The Graduate Management Admission Test (GMAT) is a standardized exam used by many universities as part of the assessment for adm
Nat2105 [25]

Answer:

a) 16% of GMAT scores are 647 or higher.

b) 2.5% of GMAT scores are 647 or higher.

c) 34% of GMAT scores are between 447 and 547.

d) 81.5% of GMAT scores are between 347 and 647.

Step-by-step explanation:

The Empirical Rule states that, for a normally distributed random variable:

68% of the measures are within 1 standard deviation of the mean.

95% of the measures are within 2 standard deviation of the mean.

99.7% of the measures are within 3 standard deviations of the mean.

In this problem, we have that:

Mean = 547

Standard deviation = 100

a. What percentage of GMAT scores are 647 or higher?

The Empirical rule states that 68% of the scores are within 1 standard deviation of the mean, that is, from 547 - 100 = 447 to 547 + 100 = 647. So 32% of the scores are outside the interval. Since the distribution is symmetric, 16% of them are lower than 447 and 16% of them are higher than 647.

So

16% of GMAT scores are 647 or higher.

b. What percentage of GMAT scores are 747 or higher (to 1 decimal)?

The Empirical rule states that 95% of the scores are within 2 standard deviations of the mean, that is, from 547 - 2*347 = 347 to 547 + 2*100 = 747. So 5% of the scores are outside the interval. Since the distribution is symmetric, 2.5% of them are lower than 347 and 2.5% of them are higher than 757

So

2.5% of GMAT scores are 647 or higher.

c. What percentage of GMAT scores are between 447 and 547?

447 is one standard deviation below the mean. The Empirical rule states that 68% of the scores are within 1 standard deviation of the mean, and since the distribution is symmetric, 34% are within one standard deviation below the mean and the mean, and 34% are within the mean and one standard deviation above the mean.

547 is the mean

447 is one standard deviation below the mean

So 34% of GMAT scores are between 447 and 547.

d. What percentage of GMAT scores are between 347 and 647 (to 1 decimal)?

The easist way is adding the percentage of scores from 347 to the mean(547) and the mean to 647.

Between 347 and 547

347 is two standard deviations below the mean. The Empirical rule states that 95% of the scores are within 2 standard deviations of the mean, and since the distribution is symmetric, 47.5% are within two standard deviation below the mean and the mean, and 47.5% are within the mean and two standard deviations above the mean.

So 47.5% of the scores are between 347 and 547

Between 547 and 647

447 is one standard deviation above the mean. The Empirical rule states that 68% of the scores are within 1 standard deviation of the mean, and since the distribution is symmetric, 34% are within one standard deviation below the mean and the mean, and 34% are within the mean and one standard deviation above the mean.

So 34% of the scores are between 547 and 647.

Between 347 and 647

47.5 + 34 = 81.5% of GMAT scores are between 347 and 647.

7 0
2 years ago
A researcher evaluates the significance of a multiple-regression equation and obtains an F-ratio with df = 2,24. How many partic
alisha [4.7K]

Answer:

N=27 participants

Step-by-step explanation:

Analysis of variance (ANOVA) "is used to analyze the differences among group means in a sample".  

The sum of squares "is the sum of the square of variation, where variation is defined as the spread between each individual value and the grand mean"  

When we conduct a multiple regression we want to know about the relationship between several independent or predictor variables and a dependent or criterion variable.

If we assume that we have k independent variables and we have  j=1,\dots,j individuals, we can define the following formulas of variation:  

SS_{total}=\sum_{j=1}^n (y_j-\bar y)^2  

SS_{regression}=SS_{model}=\sum_{j=1}^n (\hat y_{j}-\bar y)^2  

SS_{error}=\sum_{j=1}^n (y_{j}-\hat y_j)^2  

And we have this property  

SST=SS_{regression}+SS_{error}  

The degrees of freedom for the model on this case is given by df_{model}=df_{regression}=k=2 where k =2 represent the number of variables.

The degrees of freedom for the error on this case is given by df_{error}=N-k-1=24. Sinc we know k we can find N.

N=24+k+1=24+2+1=27

And the total degrees of freedom would be df=N-1=27 -1 =26

On this case the correct answer would be N=27 participants

6 0
2 years ago
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