# Math

posted by .

How many combinations are there when you can buy four books from a choice of 6 books>

• Math -

Combinations = n!/r!(n-r)!

where n is the number of things to choose from, and you choose r of them
(No repetition, order doesn't matter)

5 factorial = 5! = 5 * 4 * 3 * 2 * 1 = 120

I'll let you do the calculations.

## Respond to this Question

 First Name School Subject Your Answer

## Similar Questions

1. ### algebra

John has 36 books in his locker. He has text books,library books, and telephone books. How many books of each kind does he have if: lib + tel= 2x text books and text + tel = 3x lib books I think it'd be easier to let T,L and B denote …
2. ### Pre-Algebra [Combinations]

Need help with these- 1.How many groups of 4 fabrics can be selected from 7 fabrics?
3. ### math

lara arranged the books in her bookshelf by size. 2/10 of the books were tall and 1/2 of the books were medeium sized. If 12 of the books were small, how manyu total books did she arrange?
4. ### pre calc

A math teacher uses four algebra books, two geometry books, and three pre-calculus books for reference. In how many ways can the teacher arrange the books on the shelf if books coiver the same subject matter are kept together?
5. ### math

Of 30 books (15 novels, 10 history books and 5 math books), how many ways can you get a bunch of four books to give to a friend?
6. ### Reading

Rosalind Wiseman books Terra Elan McVoy books Susane Colasanti books Elizabeth Scott books Wendelin Van Draanen books Laura Preble books Piper Banks books Melissa Kantor books Kate Brian books Katie Finn books Pamela Wells books Cathy …
7. ### math

for every 20 math books a school buys, they they get 7 aditional books for free. The school needs 297 math books. What is the total number of math books the school must buy in order to receive 297 math books in all?
8. ### MATHS

Mrs.Koh purchased new books for the school library, of which 6 were Mathematics books, 7 were Science books, 10 were Music books, 3 were Art books, and 4 were social studies books. All of these books were different. She picked a book …
9. ### math

A student has 4 English books,3 math books,and 5 history books.In how many ways can these books be arranged on a shelf if the books in same subjects must be kept together?
10. ### math

John has \$20 to spend at a used bookstore. He wants to buy twice as many science fiction books as mystery books. Mystery books sell for \$1.25. Science fiction books sell for \$1.75. Tax is included in the prices. What is the greatest …

More Similar Questions

Post a New Question