If the question doesn't talk about telephones, then the First digit can't be a 0.

Example:How many four-digit even number are there if the same digit cannot be used twice?

If the question talks about telephones then the first digit can be a 0.

Example:

2) The last part of your telephone number contain four digit how many such four-digit number there

10 * 10 * 10 * 10

__ __ __ __ = 10000

When the questions deal with Letters,In the rules , it can't be repeated nomatter what.

Example:

How many ways can the letters of the word FERMAT be arranged?

6 *5 *4*3*2*1

_ _ _ _ _ _ = 720

it can be display as 6!

Another faster way would be:

This way is called "Pick" Formula

nPr = n!/(n-r)!

n is the number of objects available to be arranged

r is the number of objects that are being arranged

6P6= 6!/(6-6)!= 6!/0!=720

When the question has the same letters, you would have to put them to together , because they can't be switch around, its impossible.

Example:

BOOK

4!/2! = 12

4!: is the numbers of letters.

2!: is the numbers of the same letters.

Remember when enter this question on the calculator you would have to be careful.

Example:

Putting this on calculator is correct:

11!/(2!4!4!)

Putting this on caluclator is incorrect:

11!/2!4!4!

This comment has been removed by the author.

ReplyDeletewaaa!. but i was the scribe last week.....

ReplyDelete