How many 4-digit numbers can be formed using 5, 6, 7 and 8 if the digits cannot be repeated?

Question

How many 4-digit numbers can be formed using 5, 6, 7 and 8 if the digits cannot be repeated?

If they are 3-digit numbers to be formed, they will be 4!=24. How about 4-digit numbers?

Answer 1

4 things taken 4 at a time can be arranged in 4! ways = 24 ways

 

4 things taken 3 at a time can be arranged in 4* 3*2 = 24 ways