Question

Without repeating, how many four digit numbers can be written using the digits.4,6,7,9?try to write these numbers.what about the digits 3,7,0,5?... examples

Answer 1

24 numbers can be written by without repeating the digits

Answer 2

Answer:

1st case: 24 numbers
2nd case: 18 numbers

Step-by-step explanation:

This is a question related to permutations.

Here, we have been given four numbers 4,6,7,9 and are asked to write the total number of four digit numbers that can be written using these numbers.

∴ Using permutation, the total number of four digit numbers that can be formed using 4,6,7,9 without repetition
⇒ 4!= 4×3×2×1
= 24 numbers.

Now, we've been given four numbers 3,7,0,5 and are asked to find out the number of four digit numbers that can be formed using these numbers.

∴ Using permutation, the number of four digit numbers that can be formed using 3,7,0,5 without repetition
= 3×3×2×1
= 18 numbers.
(Note: The ones' place can only be filled by the numbers 3,7 and 5. Thus, there are 3 ways of filling it.)