Question

Area codes are made up of three - digit numbers
a. if all numbers can be used for each digit, how many area codes are possible?
b. how many area codes would be possible if repetition is not allowed?

Answer 1

@mathmate @mayankdevnani @Anaise @myininaya

Answer 2

a. 000 to 999 makes for 1000 codes possible

Answer 3

@math&ing001 whats the answer for b please

Answer 4

When you talk about repetition do you mean all digits repeated like 555 or do we consider it repetition with just two digits like 220 ?

Answer 5

don't know what they mean but its asking for how many area codes can be made without repeating one or another

Answer 6

Well then, we remove from 1000 all possibilities with repetition.
We remove 10 possibilities for repetitions of 3 digits 000, 111, 222...
Which makes 990 possibilities.