What are the 9 different two-digit numbers that can
be formed using the digits 3,4 and 8?
To make a two digit number think of there
being two blanks to fill in, like this:
_ _
We can choose to fill in the
first blank in these 3 ways
3 _
4 _
8 _
For each of those 3 ways to fill in the the first
digit, there are 3 ways to fill in the second blank:
For 3 _ the three ways to fill in the second blank
are:
3 3
3 4
3 8
For 4 _ the three ways to fill in the second blank
are:
4 3
4 4
4 8
For 8 _ the three ways to fill in the second blank
are:
8 3
8 4
8 8
That's why there are 3 times 3 or 9 ways to fill
in the two blanks. 3 ways for the first digit,
times 3 ways to fill in the second digit.
33, 34, 38, 43, 44, 48, 83, 84, 88
Edwin
