Factorial
The notation 4! is used as an abbreviation for the product 4 * 3 * 2 * 1 so that 4! = 24.
Similarly, 9! = 9 * 8 * 7 * 6 * 5 * 4 * 3 * 2 * 1 * = 362880.
Work out:
3!
10!
100!/98!
A box of biscuits
A box of biscuits contains 36 biscuits. 20 biscuits have foil wrappers. 15 are chocolate biscuits with foil wrappers. If 9 are not chocolate and do not have a foil wrapper, then how many chocolate biscuits are there?
1) 3! = 3 x 2 x 1 = 6
ReplyDelete2) 10! = 10 x 9 x 8 x 7 x 6 x 5 x 4 x 3 x 2 x 1. From the example, 9! = 362880 so then 10 factorial is just 9! x 10 = 3628800
3) 100!/98! = 100 x 99 = 9900
I thought / meant divide not subtract. Are you sure / means subtract?
Delete'/' does mean divide and in the question, they mean divide too. This is because 100! = 100 x 99 x 98! so then when you divide, it cancels out the 98! and you are left with 100 x 99 = 9900
DeleteThat is because 100! is 100 x 99 x 98 x 97 x 96 x 95 x .... 3 x 2 x 1
DeleteNot:
100 + 99 + 98 + 97 + 96 + 95 + ... 3 + 2 + 1