OpenStudy (anonymous):

I need help PLEASE! Shelly, Jess, and Andrea are all working at an amusement park for the summer. The manager finds out that one of them left the key in the door to the security office. When he asked them who did it, they replied: Shelly: Andrea did it. Jess: Shelly did not do it. Andrea: I didn’t do it. The manager believed Jess. Use an indirect proof to show that Shelly did not leave the key in the security office door. Hint: Begin by assuming Shelly did leave the key in the door.

6 years ago
OpenStudy (anonymous):

i think you answered the wrong question

6 years ago
OpenStudy (anonymous):

Still need help?

6 years ago
OpenStudy (anonymous):

6 years ago
OpenStudy (anonymous):

Jess did not do it. Assuming she did do it,then Shelly's statement that she did it would be true. If this was true, Shelly did not do it, and Andrea's statement that says Jess did not do it would go against Shelly's, so Jess did not do it

6 years ago
OpenStudy (anonymous):

hello? you still there? understand the problem now?

6 years ago
OpenStudy (anonymous):

no i dont understand the problem because the problem states to begin as assuming that shelly left the key in the door??

6 years ago
ganeshie8 (ganeshie8):

For an indirect proof, assume that $$\textbf{Shelly left the keys}$$. Assuming Shelly left the keys, Shelly's statement that Andrea did is FALSE. Assuming Shelly left the keys, Jess's statement that Shelly did not leave is FALSE. Finally, assuming that Shelly left the keys, Andrea's statement that Andrea didnt do it is TRUE. Since two of the three given statements contradict the assumption, the assumption is false, its opposite is true. $$\textbf{Shelly did not leave the keys!}$$

6 years ago
ganeshie8 (ganeshie8):

does that help/make sense @Alexzandria6

6 years ago
OpenStudy (anonymous):

yes thank you again!!!!!!

6 years ago
ganeshie8 (ganeshie8):

np... just revised my notes. these are good proofs :D

6 years ago
ganeshie8 (ganeshie8):

tag me if you havr more of questions this kind !(:

6 years ago