Last year, nine employees of an electronics company retired. Their ages at retirement are listed below. 56, 65, 62, 53, 68, 58, 65, 52, 56 Find the standard deviation of this sample to two decimal place.

Sample standard deviation = 5.75

Step-by-step explanation:

Consider X = 56, 65, 62, 53, 68, 58, 65, 52, 56

The formula to calculate the sample standard deviation is:

To compute the sample standard deviation, sample mean is required which can be calculated as:

Thus, the sample standard deviation can be calculated as:

Hence, the sample standard deviation is 5.75.

The correct answer is:

15 bicycles and 6 skateboards.

Explanation:

Let x represent the number of bicycles and y represent the number of skateboards.  The first equation in our system is then

x+y = 21, since there are 21 total items in the shop.

Each bicycle has 2 tires and each skateboard has 4; this gives us the equation

2x+4y=54 (because they are ordering 54 tires).

This makes our system

We will use elimination to solve this; we first need one of the variables to have the same coefficient in both equations.  We will make x the same, and we will do this by multiplying the first equation by 2:

Now we will subtract the second equation from the first one:

Divide both sides by -2:

-2y/-2 = -12/-2

y = 6

There were 6 skateboards.  Substituting this into the first equation,

x+6 = 21

Subtract 6 from each side:

x+6-6 = 21-6

x = 15

There were 15 bicycles.