Question

When 100 engines are shipped, all of them are free of defects. Select a written description the complement of the given event

A) At most one of the engines is defective.
B) All of the engines are defective.
C) At least one of the engines is defe
D) None of the engines are defective

Answer 1

Option C

Explanation:

Suppose that we have a given proposition p

We define the complement as:

"NOT p" or ¬p

So, if p is:

the dog is red

the complement is

the dog is NOT red.

The principal rule to work with this is:

if p is true, then ¬p is false

if p is false, then ¬p is true.

Here the proposition is:

p = "When 100 engines are shipped, all of them are free of defects."

When this is this is true, ¬p must be false.

when this is false, ¬p must be true.

Let's analyze the given options, first the incorrect ones:

A: "At most one of the engines is defective."

here if we have for example, two defective engines, then this proposition and the original proposition are false.

B: " All of the engines are defective."

Here if there is one defective engine, then this is false, and also is the original proposition.

D: "None of the engines are defective"

When the original proposition is true "When 100 engines are shipped, all of them are free of defects.", this proposition is also true (because none of the engines are defective)

Finally, the corrrect one

C "At least one of the engines is defective"

When the original proposition is true, there are no defective engines, so this is false.

While, if this is true, there is at least one defective engine, so the original proposition is false.

Then this is the correct option:

¬p = "At least one of the engines is defective"