The Average of Three

There are three numbers. The first two are 2/3 and 3/4.

What does the third number have to be to make the average of all three be 2?

4 7/12

In order for the average of three numbers to be 2, they must all add up to 6. That gives you this equation:
2/3 + 3/4 + n = 6

Solve for n = 55/12, or 4 7/12.

Posted in Brain Teasers

Invisible Walls

What invention lets you look right through a wall?

A window.

Posted in Riddles

Lies Behind Stars

It cannot be seen, it cannot be felt,
Cannot be heard, cannot be smelt,
Lies behind stars and under hills,
And empty holes it fills.
Comes first follows after,
Ends life kills laughter.

Darkness.

Posted in Riddles

The Sun Bakes Them

The sun bakes them,
The hand breaks them,
The foot treads them,
The mouth tastes them.

Grapes. Grapes are grown in the sun, can be hand picked and crushed by feet (which is sort of gross) to make wine, which is tasted by your mouth when you drink it.

Posted in Riddles

Starts and Ends with E

What starts with “e”, ends with “e” and has one letter in it?

Envelope. Eye is a potential alternative. When spoken out loud it sounds like a single letter (I).

Posted in Riddles

Mario’s Racing Grandma

Mario is testing out a new car at the racetrack. His grandmother took it for a mile lap and averaged 30mph. How fast does Mario have to drive in the second lap to average 60mph for the two miles?

90mph is an alluring answer, but it’s impossible. At 90mph the second lap would take 40 seconds. If Grannie’s first lap at 30mph took 2 minutes, traveling 2 miles in 2 minutes and 40 seconds is an average speed of 45mph. Traveling an average speed of 60mph for 2 miles would take 2 minutes and since the grandma’s lap took all of those 2 minutes, even if Mario could break the sound barrier he wouldn’t be able to average 60mph.

Posted in Brain Teasers

A Sinking Ship

Imagine you’re alone in a boat with a large hole in the bottom. Sharks are swimming around you on all sides and the boat is sinking fast. How do you survive?

Stop imagining ;)

Posted in Brain Teasers

What Word Could Be Added to Make New Words?

What word could be added to all of these words?

apple
cone
lake
tree
ridge
nuts

Pine.

Posted in Brain Teasers

Bed, Evil, Identical

What word can be added before or after these words to make a new word or phrase?

Bed, Evil, Identical

Twin. Twin bed, Evil twin, Identical twin.

Posted in Riddles

Which Coin is Counterfeit?

You are given eight coins and told that one of them is counterfeit. The counterfeit one is slightly heavier than the other seven. Otherwise, the coins look identical. Using a simple balance scale, how can you determine which coin is counterfeit using the scale only twice?

First weigh three coins against three others. If the weights are equal, weigh the remaining two against each other. The heavier one is the counterfeit. If one of the groups of three is heavier, weigh two of those coins against each other. If one is heavier, it’s the counterfeit. If they’re equal weight, the third coin is the counterfeit.

Posted in Brain Teasers