Question

How many 3 digit numbers can be formed using 1 2 3 4 5 ? how many of these are divisible by 5?

Answer 1

Answer:

Since the number has to be Divisible by 5, the last digit of the number must be either 5 or 0. Since we have only 5, there are only 1 possibility for the last digit.

Case 1 : Assuming Repetition is allowed

⇒ One's Place = 1 possibility [ only 5 ]

⇒ Ten's Place = 5 possibilities [ 1, 2, 3, 4, 5 ]

⇒ Hundreds Place = 5 Possibilities [ 1, 2, 3, 4, 5 ]

Therefore number of ways applicable is = 5 × 5 × 1 = 25 possibilities

Case 2 : Assuming No repetition is allowed

⇒ One's Place = 1 possibility [ 5 ]

⇒ Ten's Place = 4 possibilities [ 1, 2, 3, 4 ]

⇒ Hundreds Place = 3 possibilities [ Excluding 5 and digit in tens place ]

Therefore Number of ways possible = 4 × 3 × 1 = 12 ways

This is the required answer.