- Intro to Combinations and Permutations
- Permutations with Repetition
- Permutations without Repetition
- Permutations Formula
- Android Lock Screen
- Tigers and Bears - Oh My
Combination without Repetition
- Combination Formula
- Combining Combinations
The String of Beads
- Combinations with Repetition I
- Combinations with Repetition II
Now that you know the basics of permutations, you should be able to solve the next few permutation practice problems.
License plates consist of 7 characters according to the following pattern:
- 1 non-zero digit, followed by:
- 3 letters from A-Z, followed by:
- 3 digits from 0-9.
You would like to know how many possible unique license plates can be created.
How many possible license plates can be created?
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rodrigo perezSep 28, 6:00 PM
A-Z 26 letters.
VivekNov 29, 2:42 AM
I was stupid to think that there were 27 alphabets .
BryanJan 12, 5:43 AM
Confused (again =p)! We were learning about permutations and the answer seems to be exponents?
Based on the previous nodes I would have assumed 9 * (26!/23!) * (10!/7!) would be the way to work this one out? Did I get lost somewhere along the way?
LearnerooJan 12, 8:02 AM
These are practice challenges for what was covered until now, not just the last page. "Permute" is only used when one less element becomes available each time, but here you can re-use the same characters. See Permutations with Repetition for more.