.

[BigJ]

Solved, thanks

 

[BigPoppa]

Can you use the digits once or many times?

 

[BigJ]

Originally posted by: BigPoppa
Can you use the digits once or many times?

Once

 

[TuxDave]

Originally posted by: BigJ
Alright, I admit defeat. My brother's 9th grade Math class has beaten me. Funny I can do Calc 1 Stuff just fine but I'm beaten by a simple 9th grade math problem. It goes something like this:

Picking numbers from the set 0,2,4,6,8, how many 4 digit numbers can be formed that are less than 4,000. 0 can be the first digit. Also, how many numbers can be made total. Use each digit only once.

Yes I know, I'm an idiot.

Unless there's some trick to this, I don't see where's the hard part?

First digit must be 0 or 2, then you pick 3 digits out of the 4 remaining digits?

2*4*3*2 = 8*6 = 48

As for how many total, isn't it just 5*4*3*2 = 20*6 = 120?

 

[dullard]

You just need a sheet of paper and some time. You will eventually reach the correct answer without any knowledge of statistics. Just start writing, and then count. One question - can you use a number multiple times? I'm assuming you cannot. Here are numbers you can use:

One digit numbers:
0, 2, 4, 6,8 - there are 5 of these

Two digit numbers:
02, 04, 06, 08, 20, 24, 26, 28, 40, 42, 46, 48, 60, 62, 64, 68, 80, 82, 84, 86 - there are 5*4 = 20 of these

Three digit numbers:
024, 026, 028, 042, 046, 048, 062, 064, 068, 082, 084, 086, etc - there are 5*4*3 = 60 of these

Do you see the pattern yet?

Four digit numbers:
0246, 0248, 0264, 0268, 0284, 0286, etc. - there are 2*4*3*2 = 48 of these.

Normally you'd use a 5 to start with, but that gives numbers>4000 so the pattern needed to be altered. Your final answer is 5*4*3*2 = total 4 digit combinations, 2*4*3*2 = total 4 digit combinations under 4000.

 

[TuxDave]

Weird, I thought he said the numbers had to be 4 digits? Ahh... nm, I see the edit.

 

[dullard]

Originally posted by: TuxDave
Weird, I thought he said the numbers had to be 4 digits? Ahh... nm, I see the edit.

I was trying to show how he could come up with the formula without any thought. I didn't make it clear enough the first time.

 

[BigJ]

Originally posted by: dullard
You just need a sheet of paper and some time. You will eventually reach the correct answer without any knowledge of statistics. Just start writing, and then count. One question - can you use a number multiple times? I'm assuming you cannot. Here are numbers you can use:

One digit numbers:
0, 2, 4, 6,8 - there are 5 of these

Two digit numbers:
02, 04, 06, 08, 20, 24, 26, 28, 40, 42, 46, 48, 60, 62, 64, 68, 80, 82, 84, 86 - there are 5*4 = 20 of these

Three digit numbers:
024, 026, 028, 042, 046, 048, 062, 064, 068, 082, 084, 086, etc - there are 5*4*3 = 60 of these

Do you see the pattern yet?

Four digit numbers:
0246, 0248, 0264, 0268, 0284, 0286, etc. - there are 2*4*3*2 = 48 of these.

Normally you'd use a 5 to start with, but that gives numbers>4000 so the pattern needed to be altered. Your final answer is 5*4*3*2 = total 4 digit combinations, 2*4*3*2 = total 4 digit combinations under 4000.

Thats what I thought it was, but I was only like 90% sure and didnt want my brother to get the wrong answer.

 

[Ameesh]

2*4*3*2=48

you have 2 choices for the first number as it needs to be under 4K (it could be 0 or 2)

the number must be 4 digits long and you can only use each digit once

the set has 5 numbers total and you used 1 of the digits

so you have 3 place holders left and 4 different digits to work with

hence 2*4*3*2

 

[rudder]

Originally posted by: BigJ
Solved, thanks

no problem. Glad I could help.

 

Grrrr! Why do people always do the dreaded dot thing? I was looking for this thread to read or post to, since I couldn't respond to the question this morning. I remembered the word permutation was on keyword, but I still got no results in search! Anyway, it would be helpful if some people would just leave the title and add "Solved", "Please lock", etc. rather than delete the entire subject title. This same question may prove helpful to another member in the future or present.

I'm glad you got the problem solved, in any case.

 

[Evadman]

luvly, please take a deep breath in though your nose, and out though your mouth. Repeat until you feel better.

 

[Fudssa]

 

[Fudssa]

Originally posted by: dullard
You just need a sheet of paper and some time. You will eventually reach the correct answer without any knowledge of statistics. Just start writing, and then count. One question - can you use a number multiple times? I'm assuming you cannot. Here are numbers you can use: One digit numbers: 0, 2, 4, 6,8 - there are 5 of these Two digit numbers: 02, 04, 06, 08, 20, 24, 26, 28, 40, 42, 46, 48, 60, 62, 64, 68, 80, 82, 84, 86 - there are 5*4 = 20 of these Three digit numbers: 024, 026, 028, 042, 046, 048, 062, 064, 068, 082, 084, 086, etc - there are 5*4*3 = 60 of these Do you see the pattern yet? Four digit numbers: 0246, 0248, 0264, 0268, 0284, 0286, etc. - there are 2*4*3*2 = 48 of these. Normally you'd use a 5 to start with, but that gives numbers>4000 so the pattern needed to be altered. Your final answer is 5*4*3*2 = total 4 digit combinations, 2*4*3*2 = total 4 digit combinations under 4000.

What he said.

 

[OIKOS]

keep the topic up..!

 

[Rent]

Originally posted by: OIKOS
keep the topic up..!

why?

 

[OIKOS]

Originally posted by: Rent

Originally posted by: OIKOS
keep the topic up..!

why?

..... CUZ I AM OIKOS!! :| lol... jk... iono..