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3 years ago

Question 20 please thank hou

Mathematics

1 answer:

Mekhanik [1.2K]3 years ago

8 0

$\dfrac{9mn-6m}{25-m^2}\div\dfrac{12mn}{5+m}=\dfrac{3m(3n-2)}{5^2-m^2}\cdot\dfrac{5+m}{3m\cdot4n}\\\\=\dfrac{3n-2}{(5-m)(5+m)}\cdot\dfrac{5+m}{4n}=\dfrac{3n-2}{4n(5-m)}\to\boxed{C.}$

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48. Reading Rates The reading speed of sixth-grade students is approximately normal, with a mean speed of 125 words per minute a

son4ous [18]

Answer:

The reading speed of a sixth-grader whose reading speed is at the 90th percentile is 155.72 words per minute.

Step-by-step explanation:

Problems of normally distributed samples are solved using the z-score formula.

In a set with mean $\mu$ and standard deviation $\sigma$ , the zscore of a measure X is given by:

$Z = \frac{X - \mu}{\sigma}$

The Z-score measures how many standard deviations the measure is from the mean. After finding the Z-score, we look at the z-score table and find the p-value associated with this z-score. This p-value is the probability that the value of the measure is smaller than X, that is, the percentile of X. Subtracting 1 by the pvalue, we get the probability that the value of the measure is greater than X.

In this problem, we have that:

$\mu = 125, \sigma = 24$

What is the reading speed of a sixth-grader whose reading speed is at the 90th percentile

This is the value of X when Z has a pvalue of 0.9. So it is X when Z = 1.28.

$Z = \frac{X - \mu}{\sigma}$

$1.28 = \frac{X - 125}{24}$

$X - 125 = 1.28*24$

$X = 155.72$

The reading speed of a sixth-grader whose reading speed is at the 90th percentile is 155.72 words per minute.

4 0

3 years ago

Read 2 more answers

How many miles per gallon does the car get

Diano4ka-milaya [45]

Answer:

25 miles for 1 gallon

Step-by-step explanation:

Looking at the graph, for 1 gallon of gas, is about 25 miles. For 2 gallons, it is 50 miles. For 3 gallons, it is 75 miles. So based on the graph and the pattern, we can assume 1 gallon of gas will take the car 25 miles.

5 0

2 years ago

A man walks at 60km/ hr. How long does he walks between 9:30 am and 12 noon

N76 [4]

Answer:

He walks 150 km in 2.5 hours.

Step-by-step explanation:

From 9:30 a.m. to noon, it's 2.5 hours.

distance = speed * time

distance = 60 km/h * 2.5 h

distance = 150 km

Answer: He walks 150 km in 2.5 hours.

3 0

2 years ago

A circle has a circumference of 28π centimeters. In terms of π, what is the area of the circle to the nearest square centimeter?

Vadim26 [7]

Hi there!

The formula to find the are of a circle is :

a = $\pi$ r²

The formula to find the circumference of a circle is :

c = 2 $\pi$ r

In order to use the area formula, you need to figure out what the radius (r) is.

If we solve for "r" in the circumference equation, we have :

r = c ÷ (2 $\pi$ )

Now we use this to replace "r" in the area formula :

a = $\pi$ ( c ÷ (2 $\pi$ ))²

When we simplify this we get :

a = c² ÷ 4 $\pi$

Now you can put your value of "c" into this equation and find "a".

*Remember, $\pi$ is about 3.1416.

Solving for "a" :

a = c² ÷ 4 $\pi$

a = 28² ÷ 4 $\pi$

28² = 28 × 28 = 784

a = 784 ÷ 4 $\pi$

4 $\pi$ = 4 × $\pi$ = 12.56637061435917

a = 784 ÷ 12.56637061435917

a = 62.38873769202297cm²

You need to round to the nearest square centimeter, which means that you need to round to the nearest whole number :

a = 62cm²

There you go! I really hope this helped, if there's anything just let me know! :)

8 0

3 years ago

PLEASE HELP <br> What is the probability of an impossible event?

Likurg_2 [28]

Answer:

depending on the fraction you are using, or the answer is impossible.

Step-by-step explanation:

any fraction, so to speak 0/10 is an impossible probability, or 0%

8 0

3 years ago