How many five digit numbers can be formed with the digits 0, 1, 2, 3 a...
Since order matters in this question (12340 is a different number from 42310), we can solve it using either the Filling Spaces method or the Permutation formula.
Step 1: Understand the objective
The objective of the question here is to find the number of 5-digit numbers that can be formed using the digits 0, 1, 2, 3 and 4 without repeating any digit.
Step 2: Write the objective equation enlisting all tasks
One thing to note in this question is that one of the digits is 0. When the 5 digits are arranged such that the first digit is 0 (for example: 01234), the result is a 4-digit number. The question specifically asks about the number of five digit numbers only. This means that after considering all the possible permutations of the given 5 digits, we need to subtract the cases in which the first digit is 0 (which makes the number effectively a 4-digit number)
Now, in the numbers where the first digit is 0, there are 4 digits left (1, 2, 3 and 4) to be arranged in 4 spaces.
So,
This is the objective equation.
Now, we know that
The number of ways in which 5 digits can be arranged in 5 spaces = 5P5
And
The number of ways in which 4 digits can be arranged in 4 spaces = 4P4
So, the objective equation becomes:
(Number of 5-digit numbers that can be formed using the digits 0, 1, 2, 3 and 4)
= 5P5 -4P4
Step 3: Determine the number of ways of doing each task
In Step 3, using the Permutation Formula (nPn = n!), we get that
5P5 = 5! = 5*4*3*2*1 = 120
And,
4P4 = 4! = 4*3*2*1 = 24
Step 4: Calculate the final answer
By putting these valuesin the objective equation, we get:
(Number of 5-digit numbers that can be formed using the digits 0, 1, 2, 3 and 4)
= 120 – 24 = 96
Looking at the answer choices, we see that Option C is correct.