Question

Licence plates consist of either 3 letters and 3 numbers or 4 letters and 3 numbers. How many different licence plates can be issued..

Answer 1

now we have an addition because of the "OR"

Answer 2

Trying this again using nCr :

So... 26c3 + 10c3
= 3496

26c4 + 10c3
= 23751 + 220
= 23971

= 27467 ?

Answer 3

lol this nCr business is killing you i see
it does not say that you cannot repeat numbers or letters

Answer 4

oh sheesh.... so I might have been right before....and yes it really is

Answer 5

so.... 26x26x26x10x10x10 + 26x26x26x26x10x10x10
?

Answer 6

counting principle all the way
26 choices for each of 3 letters gives a total of \(26^3\) choices for the letters

Answer 7

yes

Answer 8

474552000 possibilities..

Answer 9

whatever that number is, your first answer is correct

Answer 10

phew..okay so to clarify for the 23545th time... nCr is used when there can NOT be repetition

Answer 11

@geekchloe don't be confused by "formulas" make sure to understand what exactly is the question, and apply the counting principle. it is the basis for all of these

Answer 12

yes, in general you have nCr when there cannot be repetition, such as picking marbles out of a bag and not replacing them
or dealing cards out of a deck (since you don't deal a card, put it back, and then deal another one)

Answer 13

right...that part makes sense

Answer 14

good!

Answer 15

unfortunately..i probably still have more questions. thanks :P

Answer 16

np