Like what you saw?
Create FREE Account and:
 Watch all FREE content in 21 subjects(388 videos for 23 hours)
 FREE advice on how to get better grades at school from an expert
 Attend and watch FREE live webinar on useful topics
Permutations  Problem 3
Carl Horowitz
Carl Horowitz
University of Michigan
Runs his own tutoring company
Carl taught upperlevel math in several schools and currently runs his own tutoring company. He bets that no one can beat his love for intensive outdoor activities!
An applied case of permutations is looking at an ATM pin. But the problem we're looking at is basically an ATM pin dealing with four digits and we're trying to figure out the number of pin numbers if repetition is allowed or if repetition is not allowed.
So whenever I'm dealing with a problem like this I try to draw out my spots to give me a visual on what's going on and before we started this we actually had a debate as to if our pin number can start with 0, nobody actually knows which tells you that most people don't start it with 0, but we're going to assume that we can to give use the idea that this is a little bit more uniform than otherwise maybe.
So basically first spot, we said we can throw in 0, we're not sure if we can so we can throw in 0, 1, 2, 3, 4, 5 all the way up to 9 which gives us 10 digits so we can have 10 things going in our spot. Because repetition is allowed, there is still 10 things that can go in second 10 things, 10 in the third, 10 in the fourth giving us 10 to the fourth which is the same thing as 10,000.
What if repetition is not allowed? I still like to draw out my little slots and then basically fill in the blacks. So our first term could be anything 0 through 9 giving us 10 things. Our second, we already chose one number and when can't reuse that number again so this is just going to be 9 times 8 times 7 which given permutations is just going to be 10 permute 4. 10 permute there's 10 things available and the permutation is basically saying the 4 numbers that we're looking for.
So difference between repetition and nonrepetition when we are dealing with repetition there in no really permutation involved in terms of our formula, there is just something to a power. When repetition is not allowed, then we're dealing with a permutation just a number of things that are available to us the number of digits 0 to 9 permute a number that we actually want in this case 4. Just a slight difference between our repetition and our nonrepetition.
Please enter your name.
Are you sure you want to delete this comment?
Carl Horowitz
B.S. in Mathematics University of Michigan
He knows how to make difficult math concepts easy for everyone to understand. He speaks at a steady pace and his stepbystep explanations are easy to follow.
i love you you are the best, ive spent 3 hours trying to understand probability and this is making sense now finally”
BRIGHTSTORM IS A REVOLUTION !!!”
because of you i ve got a 100/100 in my test thanks”
Concept (1)
Sample Problems (4)
Need help with a problem?
Watch expert teachers solve similar problems.

Permutations
Problem 1 7,084 views7 runners in a race, how many different ways can they medal?

Permutations
Problem 2 6,334 viewsHow many distinct ways are there to arrange the letters in mom?

Permutations
Problem 3 5,668 viewsAn ATM pin consists of four numbers. How many pins if
a) repetition is allowed
b) repetition is not allowed 
Permutations
Problem 4 5,280 viewsHow many ways can 5 guys and 4 girls be arranged so that guys and girls must alternate?
Comments (0)
Please Sign in or Sign up to add your comment.
·
Delete