1, 2, 3

How many 3-digit even numbers are there, which comprise of all three digits 1, 2 and 3 in some order?


The answer is 2.

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9 solutions

Revanth Gumpu
Aug 18, 2013

Well there are two major ways of doing this problem. One is by listing out and finding out all even numbers comprising only these three numbers. We know that these digits do not repeat.

So: 123, 132, 213, 231, 312, 321.

Essentially, we count these and the answer we see is 2.

Another way is that since only three digits will be used without repeating digits and that it has to be even, the ones digit has to be an even integer since that is the only way any number can be presumed as even. So we 2 as our only even integer so that leaves 3 and 1 for 2 places. We have 2 times 1 which is 2 .

Moderator note:

I prefer the second way. For the number to be even, it is necessary and sufficient for the last digit to be 2.

oh how did you get it?

Pjhay Nedamla - 7 years, 9 months ago
C S
Oct 21, 2013

There are 6 combinations for 3-digit numbers containing the digits 1, 2, and 3. They are:

123 132 231 213 312 321

Of these, the only combinations that are even are:

132 312

Therefore, there are 2 even 3-digit numbers containing the digits 1, 2 and 3.

Diana Estocapio
Apr 1, 2014

There 6 ways to form the numbers 1, 2 and 3 into a three-digit number: 123, 132, 213, 231, 312, and 321. Of these numbers, there are only two even numbers, 132 and 312. Therefore the answer is 2.

Siao Chi Mok
Oct 21, 2013

Since we want to get even numbers, 2 should be the unit digit. Thus, we are left with 1 and 3, which yields 2 permutations, i.e. (1,3) and (3,1). In conclusion, there are only 2 numbers, 132 and 312.

Marcos Oliveira
Jan 3, 2014
  • xx2 ----> 2! = 2 \boxed{2}

X1 X2 X3 is the three digit no X1- can have 3 values 1,2 or 3. X2- can have 3 values 1,2 or 3. but where as the term to be even last position X3 is occupied only by 2. so total no of digits are 3 3 1=9 so 9 is the answer

Bhaskar Akash - 7 years, 3 months ago
Skully Dirt
Oct 24, 2013

132 and 312

Sam Dreilinger
Oct 20, 2013

There are 3! three-digit numbers which can be formed from the digits 1, 2, and 3. They are: 123, 132, 213, 231, 312, 321. Of these, the only even ones are 132 and 312. So the answer to this question is 2.

From the given digits 1 , 2 , 3 1, 2, 3 , a 3-digit number is formed if and only if 2 is its last digit.

This restricts us that 1 1 or 3 3 takes the hundredths or tenths place, which gives 132 132 and 321 321 . So there are 2 \fbox{2}

sorry :P that should be 312 312 instead of 321

JohnDonnie Celestre - 7 years, 9 months ago
Noreen Marpuri
Aug 19, 2013

there are six 3 digit number can be form from 1 2 3 321 312 231 213 123 132 but 312 and 132 only are even .

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