Question

A stand-up comedian uses algebra in some jokes, including one about a telephone recording that announces "You have just reached a pure imaginary number. Please multiply by i and dial again." Explain the joke.

Answer 1

When we work with imaginary numbers, we have that

i = √(-1)

then, we have that i*i = √(-1)*√(-1) = -1

An imaginary number is a number of form A + B*i, where A and B are real numbers.

Now, a purely imaginary number is a number of the form B*i, where B is a real number.

Then, if we multiply this number by i, we have that:

B*i*i = B*(-1) = -B

now we have a real number.

The joke is that now you can "reach" a real number.

Answer 2

i * i = -1

Explanation:

W hen you multiply an imaginary number or i number by another imaginary pure number, the answer is going to be a negative number, due that i *i= -1. The joke is funny because if you do what the recording is saying there you won't have a pure imaginary number and if you dial again, the same would happen again and again.