Thread: [SOLVED] Permutation and Combination Question 2

How many four-digit number greater than 5,000 can be formed from the digits 0, 1, 2, 3, 4, 5 if all digit may be repeated?

I get 215, but the answer sheet say it's 216. I don't understand. Can someone please explain?

The 1st digit must be 5 or greater, so, there's only 1 choice.
the 2nd, 3rd, 4th position can be any digit, so each for 6 choice.

So, 1 * 6 * 6 * 6 = 216
But we have to minus away 5,000 right. it's not greater than 5,000.
So 216 - 1 = 215
Am I not right?

Originally Posted by azuki

How many four-digit number greater than 5,000 can be formed from the digits 0, 1, 2, 3, 4, 5 if all digit may be repeated?

I get 215, but the answer sheet say it's 216. I don't understand. Can someone please explain?

The 1st digit must be 5 or greater, so, there's only 1 choice.
the 2nd, 3rd, 4th position can be any digit, so each for 6 choice.

So, 1 * 6 * 6 * 6 = 216
But we have to minus away 5,000 right. it's not greater than 5,000.
So 216 - 1 = 215
Am I not right?

Right.