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Is this a right deduction to make? (LG)
Posted: Tue Feb 02, 2016 10:06 am
by Lovely_Lady_In_Red_
_ _ _ (3 seats, 1,2 , and 3)
Alex, Betty, Clark
If Alex is 3rd, Betty is first.
Can I assume if Alex is 2 Betty cannot be 1?
Re: Is this a right deduction to make? (LG)
Posted: Tue Feb 02, 2016 10:18 am
by lymenheimer
You can assume that because Alex is not 3, Betty DOES NOT HAVE to be 1.
You're reading the contrapositive incorrectly.
Argument: A3 --> B1
Incorrect Contrapositive (as you are reading it): ~A3 --> ~B1
Correct Contrapositive: ~B1 --> ~A3
So if Alex is 2, Betty is still able to be 1. If Betty is 2 (or any not 1), however, Alex cannot be 3.
Re: Is this a right deduction to make? (LG)
Posted: Tue Feb 02, 2016 1:30 pm
by MAPP
Lovely_Lady_In_Red_ wrote:_ _ _ (3 seats, 1,2 , and 3)
Alex, Betty, Clark
If Alex is 3rd, Betty is first.
Can I assume if Alex is 2 Betty cannot be 1?
Here is the conditional statement: If A 3rd, then B 1st
Contrapositive: If B not 1st, then A cannot be 3rd
The only place A triggers anything is if he is in spot 3. B triggers the contrapositive if she is not in spot 1