Ok, here is another great riddle from Maria Konnikova.

And don’t miss my favorite riddle.

Can you get it without looking at the answer?

Question

If it takes 5 machines 5 minutes to make 5 widgets, how long would it take 100 machines to make 100 widgets?

Answer

If 5 machines take 5 minutes to make 5 widgets, then the output of 1 machine is 5 minutes to make 1 widget.

So let’s restate the question for clarity:

If it takes 1 machine 5 minutes to make 1 widget, how long would it take 100 machines to make 100 widgets?

The answer is 5 minutes.

1 machine makes 1 widget every 5 minutes.
2 machine makes 2 widgets every 5 minutes.
3 machine makes 3 widgets every 5 minutes.
Etc.

I discovered this question in Mastermind (Amazon), By: Maria Konnikova.

This bat and ball riddle reminded me of the riddle about the flu.

You read it and are a little confused.

But if you start with what you know, and take it step by step, it’s perfectly doable.

Question

A bat and a ball cost $ 1.10 in total.
The bat costs $ 1.00 more than the ball.
How much does the ball cost?

Answer

We have two equations with two unknowns:

Bat + Ball = $1.10
Ball + $1.00 = Bat

Therefore:

(Ball + $1.00) + Ball = $1.10

Now solve the equation for Ball:

(Ball + $1.00) + Ball = $1.10

Ball + Ball = $.10

2Ball = $.10

Ball = $.05

The ball cost $.05.
The bat cost $1.05.
The bat and ball cost $ 1.10 in total.

I discovered this question via Maria Konnikova’s book Mastermind (Amazon).