Premutations (1 Viewer)

[Halo189]

a) how many 1,2,3 or 4 digit numbers can be made using the digits 1 to 4, with no digit allowed more than once?
Ive done this part answer is 64
b) how many numbers less than 100 can be made?
cant do this part, answer is 16

thx

 

[integral95]

Lol Premutations

Anyway, clearly you can't have a 4 digit number since that's always bigger than 100.

Same goes for 3 digit numbers

So you could have any 2 digit number since that's always less than 100 and there are 4P2 possible 2 digit numbers made from digits 1 to 4

then you have to consider 1 digit numbers, it's 4P1 since you have 4 to choose from (1-4)

So the answer is 4P2 + 4P1 = 12 + 4 = 16

 

[Halo189]

Lol Premutations

Anyway, clearly you can't have a 4 digit number since that's always bigger than 100.

Same goes for 3 digit numbers

So you could have any 2 digit number since that's always less than 100 and there are 4P2 possible 2 digit numbers made from digits 1 to 4

then you have to consider 1 digit numbers, it's 4P1 since you have 4 to choose from (1-4)

So the answer is 4P2 + 4P1 = 12 + 4 = 16

Thx so simple
my teacher explained it so complicated....

 

[braintic]

I still have only ten fingers and one head, so I guess I'm a pre-mutation.