SuperPrep B Logic Game #2 Question 10 Forum

[mistd]

I don't understand the relationship between firs and maple.

[CardozoLaw09]

1.Maples --> ~Yews
2. Firs --> ~Pines
3.~Yews --> L or O (not both)
4.~(L+O) --> F +S

Combine 1. and 3. to yield: Maples -->~Yews--->L or O (not both)

10. If Firs are not in the park then from the contrapositive of 4. we know that both L and O must be in the park. If both L and O must be in the park then maples can't be in the park because that would require, from the combined conditional statements of 1. and 3. to have either L or O in the park. So by deduction Maples cannot be in the park.

[mistd]

1.Maples --> ~Yews
2. Firs --> ~Pines
3.~Yews --> L or O (not both)
4.~(L+O) --> F +S

Combine 1. and 3. to yield: Maples -->~Yews--->L or O (not both)

10. If Firs are not in the park then from the contrapositive of 4. we know that both L and O must be in the park. If both L and O must be in the park then maples can't be in the park because that would require, from the combined conditional statements of 1. and 3. to have either L or O in the park. So by deduction Maples cannot be in the park.

But how do we know that both L & O are in the park from the contrapositive of 4?
I thought the contrapositive of 4 was:

~F or ~S --> L or O

Thank you!