Permutation and combination homework

In summary, for the first question, there are 120 possible 3-digit odd numbers that can be obtained from the digits 1,2,3,4,5,6,7 without repetition. For the second question, there are 196 possible 3-digit odd numbers that can be obtained from the digits 1,2,3,4,5,6,7 with repetition allowed. The method for the second question involves considering the choices for each digit in the number.
  • #1
jinx007
62
0
Find how many 3 digits odd number that can be obtained from the digit 1,2,3,4,5,6,7 if,

1/ Repetition of digits not allowed
2/ Repetition of digits allowed

my work

1/ --- the last i digit i have control 1,3,5,7

so 2 remaining digits = 6 P 2 x 4 (4ways)

= 120

2/ i AM STUCK

In fact, i don't really know whether the method is correct,i am a bit confuse, HELPPPP

ANSWER ACCORDING TO BOOKLET :
1/ 120

2/ 196
 
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  • #2
For the second question, how many choices for the rightmost digit do you have?
After that, how many choices for the middle digit? And the first? So...
 
  • #3
nvm i gave away too much for a homework question
 

1. What is the difference between permutation and combination?

Permutation refers to the arrangement of objects where the order matters, while combination refers to the selection of objects where the order does not matter.

2. How do you calculate the number of permutations?

The number of permutations can be calculated using the formula nPr = n! / (n-r)!, where n is the total number of objects and r is the number of objects being arranged.

3. Can you give an example of a permutation problem?

An example of a permutation problem could be selecting a president, vice president, and secretary from a group of 10 candidates. The order in which they are selected would matter, making it a permutation problem.

4. How do you find the number of combinations?

The number of combinations can be calculated using the formula nCr = n! / r!(n-r)!, where n is the total number of objects and r is the number of objects being selected.

5. What is the difference between a permutation with repetition and without repetition?

A permutation with repetition allows for the same object to be selected multiple times, while a permutation without repetition does not. For example, when choosing a 3-digit code from numbers 0-9, a permutation with repetition allows for the same number to be used more than once, while a permutation without repetition would not allow for any repeated numbers.

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