Question

How many positive intergers less than 25 can be formed by using the digits 1,2,3?

Answer 1

any ideas?

Answer 2

one number you could form is the number 12

Answer 3

Is it two ways?
Because you can use 1,2 therefore 2 x 1 because you couldn't use 1 or 3 because then it wouldn't be positive?

Answer 4

well if you can use repeats, then you could have: 11, 12, 13, 21, 22, 23

if you can't use repeats, then you would only have: 12, 13, 21, 23

Answer 5

But it said positive intergers therefore only 12 & 22 work right?

Answer 6

*are the only ones that work?

Answer 7

all of the numbers I listed are positive integers

Answer 8

it will just depend on if repeats are allowed

Answer 9

Repeats are allowed, this may seem like a juvenile thing to ask but how are 11,13,21, & 23 positive? Aren't they odd?
That part confuses me but 6 ways is right because I checked in the back of the book.

Answer 10

ok so repeats are allowed, which means that there are 6 ways and they are: 11, 12, 13, 21, 22, 23

Answer 11

yes they are all positive

a number can be odd and positive (or even and positive) at the same time

Answer 12

I'm so sorry could you please explain to me how a number can be odd & positive at the same time? @jim_thompson5910

Answer 13

a number is even when it's a multiple of 2

ex: 18 is a multiple of 2 since 2*9 = 18

Answer 14

an even number could be positive or negative

ex: 18 is an even positive number, -22 is an even negative number

Answer 15

numbers like -19 and 27 are odd numbers since they are not multiples of 2

the first is a negative odd number, the second is a positive odd number

Answer 16

Oh okay I get now, thank you so much for being patient & so helpful! :) @jim_thompson5910

Answer 17

ok glad it's making sense now