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2 years ago

There are 18 boys in a class there are w fewer boys than girls how many students are there in the class

1 answer:

6 0

The Number of boys in the class is: 18

Let's call "g" to the number of girls in the class.

The problem says that there is "w" fewer boys than girls, so we have:

g-w=18

Then, the number of girls in the class is:

g=18+w

Let's call "x" to the total number of studens in the class:

x=g+18

When we substitute g=18+w into x=g+18, we obtain:

x= (18+w)+18

The total number of studens in the class is:

x=w+36

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Ashley read 30 pages last night in 20 minute. How many pages will she have read after 2 hours?

jenyasd209 [6]

Answer:

180

Step-by-step explanation:

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2 years ago

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What is the probability that a random person who tests positive for a certain blood disease actually has the disease, if we know

xeze [42]

Answer:

Step-by-step explanation:

Hello!

Any medical test used to detect certain sicknesses have several probabilities associated with their results.

Positive (test is +) ⇒ P(+)

True positive (test is + and the patient is sick) ⇒ P(+ ∩ S)

False-positive (test is + but the patient is healthy) ⇒P(+ ∩ H)

Negative (test is -) ⇒ P(-)

True negative (test is - and the patient is healthy) ⇒ P(- ∩ H)

False-negative (test is - but the patient is sick) ⇒ P(- ∩ S)

The sensibility of the test is defined as the capacity of the test to detect the sickness in sick patients (true positive rate).

⇒ P(+/S) = P(+ ∩ S)

P(S)

The specificity of the test is the capacity of the test to have a negative result when the patients are truly healthy (true negative rate)

⇒ P(-/H) = P(- ∩ H)

P(H)

For this particular blood disease the following probabilities are known:

1% of the population has the disease: P(S)= 0.01

95% of those who are sick, test positive for it: P(+/S)= 0.95 (sensibility of the test)

2% of those who don't have the disease, test positive for it: P(+/H)= 0.02

The probability of a person having the blood sickness given that the test was positive is:

P(S/+)= P(+ ∩ S)

P(+)

The first step you need to calculate the intersection between both events + and S, for that you will use the information about the sickness prevalence in the population and the sensibility of the test:

P(+/S) = P(+ ∩ S)

P(S)

P(+/S)* P(S) = P(+ ∩ S)

P(+ ∩ S) = 0.95*0.01= 0.0095

The second step is to calculate the probability of the test being positive:

P(+)= P(+ ∩ S) + P(+ ∩ H)

Now we know that 1% of the population has the blood sickness, wich means that 99% of the population doesn't have it, symbolically: P(H)= 0.99

Then you can clear the value of P(+ ∩ H):

P(+/H) = P(+ ∩ H)

P(H)

P(+/H)*P(H) = P(+ ∩ H)

P(+ ∩ H) = 0.02*0.99= 0.0198

Next you can calculate P(+):

P(+)= P(+ ∩ S) + P(+ ∩ H)= 0.0095 + 0.0198= 0.0293

Now you can calculate the asked probability:

P(S/+)= P(+ ∩ S) = 0.0095 = 0.32

P(+) 0.0293

I hope it helps!

6 0

2 years ago

4(2-x)=5(1-2x) how to solve

Semmy [17]

Answer:

13= -14x

Step-by-step explanation:

(4×2)-(4×1x)=(5×1)-(5×2x)

8-4x=5-10x

8+5=-4x-10x

13=-14x

Hopefully this will help

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2 years ago

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Factor the polynomial completetly 21b2-40b-21

ch4aika [34]

First we note symmetry in the expression's coefficients.
We also note that 7*3=21, and 7+3=10.

From the rational roots theorem, we are tempted to try with 3 and 7 as coefficients of the factors.

Try
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By switching the sign of 3b+7 to 3b-7, we get the signs right, to check:
(7b+3)(3b-7)=21b^2+(9-49)b-21=21b^2-40b-21 ....right!

So
(7b+3)(3b-7)=21b^2-40b-21

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2 years ago

Want three fractions are the same2/4 4/6 5/8 3/6 2/3 6/9

steposvetlana [31]

Answer:

2/4 . 4/6 . 2/3

Step-by-step explanation:

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