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Geometry 17 Online
OpenStudy (mndean):

Please Help! Will fan and medal! Read the proposition and the implication shown below. "If the lights are off, there is no one inside." Which statement is a contrapositive to the proposition and logically equivalent to it? side. A. If the lights are not off, there is someone in. B. If there is no one inside, the lights will not be on. C. If the lights are on, there is someone inside. D. If there is someone inside, the lights will be on.

OpenStudy (mathstudent55):

If p then q. Contrapositive: If not q, then not p.

OpenStudy (mndean):

I think it's c but I'm not sure

OpenStudy (mathstudent55):

I'll show it to you step by step. Conditional: \(If \color{red}{~the ~lights ~are ~off},~ [then]~\color{blue}{there ~is ~no ~one ~inside.}"\) The above is your given conditional.

OpenStudy (mndean):

okay thanks

OpenStudy (mathstudent55):

The red part is the hypothesis, and the blue part is the conclusion. The "if" part is the hypothesis. The "then" part is the conclusion. Still ok?

OpenStudy (mndean):

okay

OpenStudy (mathstudent55):

A typical generic conditional statement is: Conditional: \(If ~\color{red}{hypothesis},~ then~\color{blue}{conclusion.}"\) In symbols, it is: Conditional: \(If ~\color{red}{p},~ then~\color{blue}{q.}"\) where p stands for the hypothesis, and q stands for the conclusion.

OpenStudy (mathstudent55):

Keep the following in mind: p is the hypothesis q is the conclusion Conditional: If p, then q.

OpenStudy (mathstudent55):

What is the contrapositive? For a conditional, if p then q, the contrapositive is If not q, then not p.

OpenStudy (mathstudent55):

Conditional: \(If ~\color{red}{hypothesis},~ then~\color{blue}{conclusion.}"\) Contrapositive: \(If ~opposite~ of~ the~ \color{blue}{conclusion.}, ~then ~opposite~of~the~\color{red}{hypothesis}"\)

OpenStudy (mathstudent55):

Conditional: If p, then q. Contrapositive: If not q, then not p.

OpenStudy (mathstudent55):

In other words, if you start with a conditional, to find the contrapositive you need to do this: 1. switch the hypothesis and the conclusion 2. deny the hypothesis and the conclusion

OpenStudy (mathstudent55):

Back to your problem. Conditional: "If the lights are off, there is no one inside." To find the contrapositive: 1. switch the hypothesis and the conclusion If there is no inside, then the lights are off. Now deny both the hypothesis and the conclusion. If there is someone inside, then the lights are on. The last statement above is the contrapositive.

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