Homework Help Forum: 5th grade

Posted by marissa on Tuesday, October 6, 2009 at 8:44pm.

How many different four-digit numbers can you make from the digits 1,2,3, and 4 if each digit is used only once?

• 5th grade - Kelly, Tuesday, October 6, 2009 at 9:07pm

  1234 1324 1432 1243 1423 1342 2134 2143 2341 2314 2431 2413 3124 3142 3241 3214 3412 3421 4321 4312 4123 4132 4231 4213 24 there are 4 numbers...each can be used only once but 6 different ways 6x4=24

  
  

• 5th grade - Cliff, Thursday, October 8, 2009 at 9:45am

  This is a problem class known as permutations. There are 4 choices for your first number (i.e, 1,2,3,4)followed by 3 ways to pick the next number since there are only 3 numbers left. This leaves 2 ways to pick the next number and 1 way to pick the remaining number. 4*3*2*1 = 24

  
  

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