Snakes and Mice

On a remote (imaginary) island, there are 11 snakes and a single mouse. As you’d expect, snakes eat the mice. But contrary to what you’d expect, when a snake eats a mouse, it turns into one.

The snakes live by only two rules:

1. Don’t get eaten.
2. Eat mice as long as rule #1 isn’t violated.

How many snakes and mice will there be left on the island?

10 snakes, 1 mouse.

If there were only a single snake and mouse, the snake could eat the mouse, then turn into one, leaving a single mouse.

If there were two snakes and a single mouse, rule 2 would keep either of the snakes from eating the mouse to avoid being eaten themselves.

With three snakes and one mouse, one of the snakes could eat a mouse and be safe as a mouse thanks to rule 2.

This pattern continues. With an even number of snakes, nothing happens. With an odd number of snakes, one snake can eat the mouse.

Thus, with 11 snakes, one snake would eat the mouse, turn into one and leave 10 snakes and 1 mouse.

Posted in Brain Teasers

I Wear You Down

I wear you down, yet you will mourn me once I fly.
You can kill me, but I will never die.

Time.

(found in The Copper Gauntlet by Holly Black and Cassandra Clare)

Posted in Riddles

Graphical Rebus Six

What does this rebus represent?

Rebus

Waterloo Sunset

Posted in Riddles
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Debbie’s Dragster

Debbie starts driving her dragster from rest and constantly accelerates to 60 mph in 10 seconds. How far does she travel in those 10 seconds?

1/12 mile

Ten seconds is 1/6 of a minute and 1 minute is 1/60 of an hour, so 10 seconds is 1/360 of an hour.

If you graph her trip with the speed on the y-axis and the time on the x-axis, you get a triangle with height of 60 mph and width of 1/360 of an hour. To calculate the area of the triangle, you multiply 1/2 × 1/360 × 60 = 1/12.

Posted in Brain Teasers

Snail Up The Wall

A snail creeps 10 feet up a wall during the daytime, then falls asleep. It wakes up the next morning and discovers it slipped down 6 feet. If this happens each day, how many days will it take to reach the top of a 20 foot wall?

Four days.

Day 1: up to 10, down to 4
Day 2: up to 14, down to 8
Day 3: up to 18, down to 12
Day 4: up to 22 (20 really) and done

Posted in Brain Teasers

Archaeologist Laughed At

An archaeologist publicizes his find, a coin marked 649 BC, but is laughed at by his peers. Why?

No coins were ever marked BC because the BC / AD dating system wasn’t even devised until 525 AD. And it wasn’t widely used until after 800 AD.

Posted in Brain Teasers

Planting Trees on Arbor Day

On Arbor Day the fourth grade class began planting trees. They finished planting five trees before the fifth grade class arrived. But they accidentally planted them on the fifth grade side of the street.

The fourth-graders crossed the street to start over, and the fifth-graders planted the remaining trees. They finished first and felt bad for the fourth-graders, so they crossed the street and planted five trees. They planted another five trees at which point all of the trees had been planted.

By how many trees were the fifth-graders ahead of the fourth-graders?

Ten. The fifth-graders planted five more trees than they were assigned, and the fourth-graders planted five fewer than their assignment.

Posted in Brain Teasers

Not Want to Have But Not Want to Lose

What do you not want to have and not want to lose?

A lawsuit.

Posted in Riddles

Poor Sheep

A farmer had 17 sheep. All but 9 died. How many live sheep does he have left?

9. If all but 9 died, there are 9 remaining live sheep.

Posted in Brain Teasers

Springiest Anagram

What is the only anagram of Springiest?

Persisting

Posted in Brain Teasers