Question

1) Explain the difference between a Permutation and a Combination.

Answer 1

you use nPr, when you want to take note of the order, ORDER MATTERS.

Example, in choosing between A,B,C,D & E , how many ways can you choose any 3 arranged letters. (This means ABC is different from ACB or BCA or...)
Then 5P3 is the notation, or 5nPr3 is what you'd punch in the calculator


you use nCr , when the order is not important.

Example , how many ways can you get three letters from A,B,C,D & E. (here ABC is no different from BAC since you just got A&B&C.)
Then 5C3 or 5nCr3 on calculator