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3 years ago

13

Liam sits on a merry-go-round at the local fair. He completes 12 revolutions in 4

1 answer:

Musya8 [376]3 years ago

7 0

Answer:

1/3 min ( = 20 seconds)

Step-by-step explanation:

The period of the ride is the time he takes to complete 1 revolution

We are given:

12 revolutions -------> takes 4 min

1 revolution ------> takes 4/12 = 1/3 min (= 20 seconds)

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A car travels at an average speed of 68 miles per hour. How long does it take to travel 255 miles?

valentinak56 [21]

It would take 5 times because if it goes 4 times it would reach 255 miles but if it goes 5 times it will pass the amount.

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3 years ago

What is the sum of 30 1/4 + 30 1/4

yarga [219]

Answer:

60 1/2

Step-by-step explanation:

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3 years ago

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The average value of two positive numbers is 30% less than one of the two numbers. By which percentage is average value bigger t

Viefleur [7K]

Answer:

75% bigger

Step-by-step explanation:

Let the first number be x and the second be y.

So:

$Average = \frac{x + y}{2}$

And:

$Average = (1 - 30\%) * x$ -----30% less than x

Substitute $Average = (1 - 30\%) * x$ in $Average = \frac{x + y}{2}$

$\frac{x + y}{2} = (1 - 30\%) * x$

$\frac{x + y}{2} = (1 - 0.30) * x$

$\frac{x + y}{2} = 0.70 * x$

$\frac{x + y}{2} = 0.70x$

Cross multiply

$x + y = 0.70x * 2$

$x + y = 1.40x$

Collect like terms

$1.40x - x = y$

$0.40x = y$

Make x the subject

$x = \frac{y}{0.40}$

$x = 2.50y$

So, the average is:

$Average = (1 - 30\%) * x$

$Average = (1 - 30\%) * 2.50y$

$Average =0.70 * 2.50y$

$Average =1.75y$

Rewrite as:

$Average =(1 + 0.75)y$

Express as percentage

$Average =(1 + 75\%)y$

This means that the average is 75% bigger than the second number

6 0

3 years ago

The standard deviation of a sample taken from population A is 17.6 for a sample of 25.

lawyer [7]

Answer:

The standard deviation of the sample mean differences is _5.23_

Step-by-step explanation:

We have a sample of a population A and a sample of a population B.

For the sample of population A, the standard deviation $\sigma_A$ is

$\sigma_A = 17.6$

The sample size $n_A$ is:

$n_A = 25$ .

For the sample of population B, the standard deviation $\sigma_B$ is

$\sigma_B = 21.2$

The sample size $n_B$ is:

$n_B = 30$ .

Then the standard deviation for the difference of means has the following form:

$\sigma=\sqrt{\frac{\sigma_A^2}{n_A}+\frac{\sigma_B^2}{n_B}}$

Finally

$\sigma=\sqrt{\frac{17.6^2}{25}+\frac{21.2^2}{30}}\\\\\sigma= 5.23$

7 0

4 years ago