How many ways can a librarian arrange 15 books on a top shelf if she has 20 books from which to pick?

2 answers:

8 0

Use the permutation formula
nPr = (n!)/((n-r)!)
20P15 = (20!)/((20-15)!)
20P15 = (20!)/(5!)

The final answer is choice A

Inga [223]3 years ago

8 0

The correct answer is A turned this in got a 100 hoped this helped ya.

You might be interested in

Help help help help me pls !,!,!,

Len [333]

Answer:

Step-by-step explanation:

First, you find the area of RPQ using 1/2×base×height. That is, 1/2×6×8. And the answer is 24. Then you multiply 24 by 4 to get the area of all the sides excluding the base to get 96.

8 0

3 years ago

Water flows from a faucet at a constant rate. Assume that 6 gallons of water are already in a tub by the time we notice the fauc

Thepotemich [5.8K]

The equation would be y=3.2x+6

6 0

3 years ago

<img src="https://tex.z-dn.net/?f=%5Csf%20%5Clim_%7Bx%20%5Cto%20%5Cinfty%7D%20%5Ccfrac%7B%5Csqrt%7Bx-1%7D-2x%20%7D%7Bx-7%7D" id=

BARSIC [14]

<h3>Answer: -2</h3>

======================================================

Work Shown:

$\displaystyle L = \lim_{x\to\infty} \frac{ \sqrt{x-1}-2x }{ x-7 }\\\\\\\displaystyle L = \lim_{x\to\infty} \frac{ \frac{1}{x}\left(\sqrt{x-1}-2x\right) }{ \frac{1}{x}\left(x-7\right) }\\\\\\\displaystyle L = \lim_{x\to\infty} \frac{ \frac{1}{x}*\sqrt{x-1}-\frac{1}{x}*2x }{ \frac{1}{x}*x-\frac{1}{x}*7 }\\\\\\$

$\displaystyle L = \lim_{x\to\infty} \frac{ \sqrt{\frac{1}{x^2}}*\sqrt{x-1}-2 }{ 1-\frac{7}{x} }\\\\\\\displaystyle L = \lim_{x\to\infty} \frac{ \sqrt{\frac{1}{x^2}*(x-1)}-2 }{ 1-\frac{7}{x} }\\\\\\\displaystyle L = \lim_{x\to\infty} \frac{ \sqrt{\frac{1}{x}-\frac{1}{x^2}}-2 }{ 1-\frac{7}{x} }\\\\\\\displaystyle L = \frac{ \sqrt{0-0}-2 }{ 1-0 }\\\\\\\displaystyle L = \frac{-2}{1}\\\\\\\displaystyle L = -2\\\\\\$

-------------------

Explanation:

In the second step, I multiplied top and bottom by 1/x. This divides every term by x. Doing this leaves us with various inner fractions that have the variable in the denominator. Those inner fractions approach 0 as x approaches infinity.

I'm using the rule that

$\displaystyle \lim_{x\to\infty} \frac{1}{x^k} = 0\\\\\\$

where k is some positive real number constant.

Using that rule will simplify the expression greatly to leave us with -2/1 or simply -2 as the answer.

In a sense, the leading terms of the numerator and denominator are -2x and x respectively. They are the largest terms for each, so to speak. As x gets larger, the influence that -2x and x have will greatly diminish the influence of the other terms.

This effectively means,

$\displaystyle L = \lim_{x\to\infty} \frac{ \sqrt{x-1}-2x }{ x-7 } = \lim_{x\to\infty} \frac{ -2x }{ x} = -2\\\\\\$

I recommend making a table of values to see what's going on. Or you can graph the given function to see that it slowly approaches y = -2. Keep in mind that it won't actually reach y = -2 itself.

5 0

3 years ago

Because of the costs involved in maintaining high temperatures and pressure, nuclear_______________is not yet a practical method

svetoff [14.1K]

It is either nuclear energy or nuclear power.

5 0

2 years ago

Read 2 more answers

What is 45x +53u if x=7 and u=56

rewona [7]

Answer: 3,283

Step-by-step explanation: