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valleeny
- Senior | Next Rank: 100 Posts
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How many different ways can 2 students be seated in a row of 4 desks, so that there is always at least one empty desk between the students?
2
3
4
6
12
What's wrong with my method?
Number of ways = Total ways without restrictions - no. of ways where 2 students are next to each other
= 4!/2! - 3!/2!
= 12-3 = 9
wrong answer!
2! being that the position of empty chairs doesn't matter
I know there's a simpler way of simply listing out the possibilities but I prefer to do it the mathematical way
2
3
4
6
12
What's wrong with my method?
Number of ways = Total ways without restrictions - no. of ways where 2 students are next to each other
= 4!/2! - 3!/2!
= 12-3 = 9
wrong answer!
2! being that the position of empty chairs doesn't matter
I know there's a simpler way of simply listing out the possibilities but I prefer to do it the mathematical way
... so 3*2 = 6.
