Ask question

Ask question

All categories

Dennis_Churaev [7]

3 years ago

10

The ratio of boys to girls in Ella’s grade is 3 to 4. The ratio of boys to girls in Minh’s grade is 4 to 5. Each grade has a tot

al of 20 girls.

1 answer:

Aneli [31]3 years ago

4 0

Answer:

In mih's school there are 100 boys

While in Ella's school there are 80 boys

Step-by-step explanation:

X*1/5=20

X=100

X*1/4=20

X=80

You might be interested in

ANSWER QUICKLY PLEASE 2. Molecules in the air are moving with speeds based on the normal model.

raketka [301]

Answer:

(a). The mean speed is 760 m/s.

(b). The standard deviation for our normal model is 142.1 m/s.

(c). The unusual speed is 1127 m/s.

(d). The average molecule speed is 929.48 m/s.

Step-by-step explanation:

Given that,

Molecules in the air are moving with speeds based on the normal model.

Let x be the speed of the molecules.

(a). If half of the air molecules are moving faster than 760 m/s.

We can say speed of a molecules is normally distributed.

So, the mean, median and mode of this distribution is at least greater than 760 m/s.

(b). If exactly 95% of the molecules are moving with speeds between 475.8 m/s and 1044.2 m/s,

If the standard deviation is σ and the mean is μ,

We need to calculate the standard deviation for our normal model

Using empirical rule

$\mu-2\sigma=475.8$ ...(I)

$\mu+2\sigma=1044.2$ ....(II)

Put the value of μ in equation (I)

$760-2\sigma=475.8$

$-\sigma=\dfrac{475.8-760}{2}$

$\sigma=142.1\ m/s$

(c). One molecule is found to be moving with a speed of 1127 m/s.

We know that,

1127 is the between 1126 and 1128.

Since, it is a continuous distribution,

We need to find the probability that speed is between this

Using excel function

$P(1126$

$P(1126$

We know that,

Any probability less than 0.05 is considered as unusual

So, 0.0002<0.05

So, 1127 will be considered as the unusual speed.

(d). If the temperature increase caused the z-score of a particle moving at 1100 m/s particle to drop to 1.2 after the temperature increase.

We need to calculate the average molecule speed

Using formula of average molecule speed

$z=\dfrac{x-\mu'}{\sigma}$

$-\mu'=z\sigma-x$

Put the value in to the formula

$-\mu'=1.2\times142.1-1100$

$\mu'=929.48\ m/s$

Hence, (a). The mean speed is 760 m/s.

(b). The standard deviation for our normal model is 142.1 m/s.

(c). The unusual speed is 1127 m/s.

(d). The average molecule speed is 929.48 m/s.

8 0

3 years ago

You want to obtain a sample to estimate a population proportion. At this point in time, you have no reasonable preliminary estim

prohojiy [21]

Using the z-distribution, it is found that a sample size of 3,385 is required.

<h3>What is a confidence interval of proportions?</h3>

A confidence interval of proportions is given by:

$\pi \pm z\sqrt{\frac{\pi(1-\pi)}{n}}$

The margin of error is:

$M = z\sqrt{\frac{\pi(1-\pi)}{n}}$

In which:

$\pi$ is the sample proportion.

z is the critical value.

n is the sample size.

In this problem, we have a 98% confidence level, hence $\alpha = 0.98$ , z is the value of Z that has a p-value of $\frac{1+0.98}{2} = 0.99$ , so the critical value is z = 2.327.

We have no prior estimate, hence $\pi = 0.5$ is used, which is when the largest sample size is needed. To find the sample size, we solve the margin of error expression for n when M = 0.02, hence:

$M = z\sqrt{\frac{\pi(1-\pi)}{n}}$

$0.02 = 2.327\sqrt{\frac{0.5(0.5)}{n}}$

$0.02\sqrt{n} = 2.327 \times 0.5$

$\sqrt{n} = \left(\frac{2.327 \times 0.5}{0.02}\right)$

$(\sqrt{n})^2 = \left(\frac{2.327 \times 0.5}{0.02}\right)^2$

n = 3,385.

A sample size of 3,385 is required.

More can be learned about the z-distribution at brainly.com/question/25890103

#SPJ1

5 0

2 years ago

WILL GIVE BRAINLIEST

nikklg [1K]

Answer:

the answer is c

Step-by-step explanation:

2+2=4-1 that three quik mathsss

8 0

3 years ago

Read 2 more answers

Miguel wants to buy a new stereo that costs $320. He has $40 in March, $80 in April, and $120 in May. If this pattern continues,

igor_vitrenko [27]

March, April, and May correspond to 3,4, and 5th months. Each month the amount of money he saves increases by $40, so this is a constant rate of change, or constant velocity, which means that this is a linear equation. Let y=the amount of money he has and x=the month number and model it with the line of form y=mx+b, where m=slope, or rate, and b=y-intercept...

y=40x+b, we know that he has $40 on the third month (February) so:

40=40(3)+b

40=120+b

-80=b so the equation is:

y=40x-80 (note that the domain is x=[3, +oo) only for the function to have meaining)

Now you want to know when he has $320...

320=40x-80

400=40x

10=x

So he will have $320 on the 10th month, which is October.

8 0

3 years ago

A wooden bench was originally priced at $50 but went on sale for 20% off. If Presley bought the wooden bench and paid a 5% sales

Savatey [412]

Answer:

$42.00

Step-by-step explanation:

20% OF 50 = 40

Before Tax Price: $40.00

Sale Tax: 5.00% or $2.00

After Tax Price: $42.00

5 0

3 years ago

Read 2 more answers