OpenStudy (anonymous):

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

4 years ago
OpenStudy (jim_thompson5910):

any ideas?

4 years ago
OpenStudy (jim_thompson5910):

one number you could form is the number 12

4 years ago
OpenStudy (anonymous):

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?

4 years ago
OpenStudy (jim_thompson5910):

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

4 years ago
OpenStudy (anonymous):

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

4 years ago
OpenStudy (anonymous):

*are the only ones that work?

4 years ago
OpenStudy (jim_thompson5910):

all of the numbers I listed are positive integers

4 years ago
OpenStudy (jim_thompson5910):

it will just depend on if repeats are allowed

4 years ago
OpenStudy (anonymous):

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.

4 years ago
OpenStudy (jim_thompson5910):

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

4 years ago
OpenStudy (jim_thompson5910):

yes they are all positive a number can be odd and positive (or even and positive) at the same time

4 years ago
OpenStudy (anonymous):

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

4 years ago
OpenStudy (jim_thompson5910):

a number is even when it's a multiple of 2 ex: 18 is a multiple of 2 since 2*9 = 18

4 years ago
OpenStudy (jim_thompson5910):

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

4 years ago
OpenStudy (jim_thompson5910):

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

4 years ago
OpenStudy (anonymous):

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

4 years ago
OpenStudy (jim_thompson5910):

ok glad it's making sense now

4 years ago