Question

A summer reading list has 20 books on it. How many ways can you choose 4 books?

Answer 1

@SaylorTickels Do you know combinations and permutations of objects and how to calculate them?

Answer 2

no

Answer 3

Have you heard of them?

Answer 4

very vaguely

Answer 5

What you want to compute is a combination of 20 books taken 4 at a time.
That gives you the number of different groups of 4 books from the 20.
C(20,4) --> Think of this as 20 Choose 4.
We'll need the combination formula.

Answer 6

If you have not studied combinations, you can think of the problem this way:
There are 20 ways to choose the first book, 19 for the second, 18 for the third, and 17 for the last. That would give 20*19*18*17 ways where order mattered. But, the order of selection is not of importance. So, you would need to divide out the number of ways a given set of four books could be chosen in order. That is 4*3*2*1.

I have said too much but on problems of this type, words are necessary.

Here is your task: Divide (20*19*18*17) by 24 to get the answer you seek.
Note: 24 is the 4*3*2*1 part.

Answer 7

I believe there's more to it than that. A combination such as this one is \[C(20, 4) = \frac{ 20! }{ 4!(20-4)! }\]

Answer 8

wait, nvrm, they're the same

Answer 9

Directrix is using good logic. What I have is the formula definition.

Answer 10

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Answer 11

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Answer 12

Anatomy Tutorial: Cranial Meninges

Answer 13

Read the poem.

Dulce et Decorum Est
by Wilfred Owen

Bent double, like old beggars under sacks,
Knock-kneed, coughing like hags, we cursed through sludge,

Answer 14

Read the excerpt of the poem. Then answer the questions.

excerpt from ''Paul Revere's Ride''
by Henry Wadsworth Longfellow

It was twelve by the village cl

Answer 15

How much does one sucrose molecule weigh in grams?

Answer 16

Herky and Elaina want to compare their investment accounts to see how much they will have in the accounts after eight years.

Answer 17

An airplane is flying at an altitude of 2,910 m, has mass of 5,320 kg, and experiences a drag force of 530 N.

Answer 18

Archery stuffff (:
(I'm not the best of course)

Answer 19

Just want to check the word order on this assignment

Answer 20

What is the main idea?
https://ap.gilderlehrman.org/resource/thomas-jefferson%27s

Answer 21

Will flex seal work as a condom if needed?

Answer 22

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Answer 24

triangle congruences

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Answer 27

Triangle congruence

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