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2 years ago

Estimate 306.9 divided by 6.4

Mathematics

2 answers:

stich3 [128]2 years ago

8 0

Round 306.9 to 307 then divide by 6.4 then you have your answer

Illusion [34]2 years ago

7 0

Answer:

48.

Step-by-step explanation:

Given : 306.9 divided by 6.4

To find : Estimate

Solution : We have given 306.9 divided by 6.4

We can write it as $\frac{306.9}{6.4}$

On removing decimal of both number

$\frac{30690}{640}$ .

We get 47.95

After decimal number is 9 which is greater than g os it would be rounded up 48.

Therefore, 48.

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In a study of exercise, a large group of male runners walk on a treadmill for six minutes. Their heart rates in beats per minute

Vera_Pavlovna [14]

Answer:

a) 1.88% percent of the runners have heart rates above 130.

b) 50% percent of the nomrunners have heart rates above 130.

Step-by-step explanation:

Problems of normally distributed samples can be 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.

(a) What percent of the runners have heart rates above 130?

In a study of exercise, a large group of male runners walk on a treadmill for six minutes. Their heart rates in beats per minute at the end vary from runner to runner according to the N(104,12.5) distribution. This means that $\mu = 104, \sigma = 12.5$ .

This percentage is 1 subtracted by the pvalue of Z when $X = 130$ .

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

$Z = \frac{130 - 104}{12.5}$

$Z = 2.08$

$Z = 2.08$ has a pvalue of 0.9812.

This means that 1-0.9812 = 0.0188 = 1.88% percent of the runners have heart rates above 130.

(b) What percent of the nonrunners have heart rates above 130?

The heart rates for male nonrunners after the same exercise have the N(130, 17) distribution. This means that $\mu = 130, \sigma = 17$ .

This percentage is 1 subtracted by the pvalue of Z when $X = 130$ .

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

$Z = \frac{130 - 130}{17}$

$Z = 0.00$

$Z = 0.00$ has a pvalue of 0.5000.

This means that 1-0.50 = 0.50 = 50% percent of the nomrunners have heart rates above 130.

4 0

2 years ago

A batter strikes a baseball. the equation y = -0.005^2 +0.7x + 3.5 models its path, where x is the horizontal distance, in feet,

hram777 [196]

Answer:

(D)144.8 feet

Step-by-step explanation:

Given the equation which models the path of the baseball

$y = -0.005x^2 +0.7x + 3.5$

where x is the horizontal distance, in feet, the ball travels and y is the height, in feet, of the ball.

To determine how far from the batter the ball will land, we determine the distance x at which the height, y=0.

$y = -0.005x^2 +0.7x + 3.5=0$

$-0.005x^2 +0.7x + 3.5=0$

We use the quadratic formula to solve.

In the quadratic equation above, a=-0.005, b=0.7, c=3.5

$x=\dfrac{-b\pm\sqrt{b^2-4ac} }{2a} \\=\dfrac{-0.7\pm\sqrt{0.7^2-4(-0.005*3.5)} }{2*-0.005} \\=\dfrac{-0.7\pm\sqrt{0.49+0.07} }{-0.01}\\=\dfrac{-0.7\pm\sqrt{0.56} }{-0.01}\\x=\dfrac{-0.7+\sqrt{0.56} }{-0.01} \: or\: x=\dfrac{-0.7-\sqrt{0.56} }{-0.01}\\x=-4.83 \: or\: x=144.83$

Since x cannot be negative, x=144.8 feet to the nearest tenth of a foot.

<u>The correct option is D.</u>

6 0

2 years ago

Caleb has 1/3 of a watermelon. He cuts it into 4 equal pieces. What fraction of the watermelon is each piece

polet [3.4K]

Answer:

1/12 of the watermelon in each piece

Step-by-step explanation:

We must divide 1/3 by 4.
1/3 divided by 4 is also 1/3 x 1/4.

The final answer is 1/12.

<em>I hope this helped!</em>

5 0

2 years ago

Read 2 more answers

It is believed that as many as 23% of adults over 50 never graduated from high school. We wish to see if this percentage is the

JulijaS [17]

Answer:

1) n=48

2) n=298

3) n=426

Step-by-step explanation:

Previous concepts

A confidence interval is "a range of values that’s likely to include a population value with a certain degree of confidence. It is often expressed a % whereby a population means lies between an upper and lower interval".

The margin of error is the range of values below and above the sample statistic in a confidence interval.

Normal distribution, is a "probability distribution that is symmetric about the mean, showing that data near the mean are more frequent in occurrence than data far from the mean".

$p$ represent the real population proportion of interest

$\hat p$ represent the estimated proportion for the sample

n is the sample size required (variable of interest)

$z$ represent the critical value for the margin of error

The population proportion have the following distribution

$p \sim N(p,\sqrt{\frac{\hat p(1-\hat p)}{n}})$

Part 1

In order to find the critical value we need to take in count that we are finding the interval for a proportion, so on this case we need to use the z distribution. Since our interval is at 90% of confidence, our significance level would be given by $\alpha=1-0.90=0.10$ and $\alpha/2 =0.05$ . And the critical value would be given by:

$z_{\alpha/2}=-1.64, z_{1-\alpha/2}=1.64$

The margin of error for the proportion interval is given by this formula:

$ME=z_{\alpha/2}\sqrt{\frac{\hat p (1-\hat p)}{n}}$ (a)

And on this case we have that $ME =\pm 0.1$ and we are interested in order to find the value of n, if we solve n from equation (a) we got:

$n=\frac{\hat p (1-\hat p)}{(\frac{ME}{z})^2}$ (b)

We can assume that the estimated proportion is 0.23 for the 25 to 30 group. And replacing into equation (b) the values from part a we got:

$n=\frac{0.23(1-0.23)}{(\frac{0.1}{1.64})^2}=47.63$

And rounded up we have that n=48

Part 2

The margin of error on this case changes to 0.04 so if we use the same formula but changing the value for ME we got:

$n=\frac{0.23(1-0.23)}{(\frac{0.04}{1.64})^2}=297.7$

And rounded up we have that n=298

Part 3

In order to find the critical value we need to take in count that we are finding the interval for a proportion, so on this case we need to use the z distribution. Since our interval is at 95% of confidence, our significance level would be given by $\alpha=1-0.95=0.05$ and $\alpha/2 =0.025$ . And the critical value would be given by: