Lending Money to Darlene

Franklin lent Darlene as much money as she already had, then she spent $10. The next day, Franklin lent her as much money as she now had and again, she spent $10. On the third day Franklin once again lent her as much money as she now had and she spent $10, leaving her broke. How much money did Darlene start with?

$8.75
You may have been tempted to guess $30 because $10 is spent three times, but that would mean she would have had $60 ($30 lent plus the $30 she already had), and $50 after spending $10. The rest of the numbers end up at higher than zero, so we know it has to be less than $30. Even starting at $10 leaves Darlene with $10 on the third day. Starting with $8.75 works out as follows.

Day 1: $8.75 (lent) + $8.75 (already had) – $10 (spent) = $7.50 (remaining)
Day 2: $7.50 + $7.50 – $10 = $5
Day 3: $5 + $5 – $10 = $0

Posted in Brain Teasers

One Two Six Sequence

What is the next number in this series?

1, 2, 6, 42, 1806, ___

To get the next number, multiply the previous number in the series by itself plus one:

n × (n + 1).

For example, to get 6, multiply 2 × (2 + 1)
To get 42 multiply 6 × (6 + 1)

Thus, 1806 × 1807 = 3263442

Posted in Brain Teasers
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Nine-Letter Word, Common as Air

A nine-letter word, common as air,
When each letter’s cut, a new word to pare,
Take a letter each round and continue to one.
Name the word and the path and then you’ll be done.

Surprisingly, there are several nine-letter words that can have one letter removed in each round to make a new word all the way to one letter, which must be ‘a’ or ‘i’. Startling is the most common answer, but I’ve included the other words I’m aware of. I don’t include plural words, like cleansers, drownings, splatters, starvings, trappings and wrappings because it’s kind of cheating.

startling
Remove the l to make starting (or remove the t to make starling)
Remove the t to make staring
Remove the a to make string
Remove the r to make sting
Remove the t to make sing
Remove the g to make sin
Remove the s to make in
Remove the n to make I

splitting
Remove the l to make spitting
Remove the p to make sitting
Remove a t to make siting
Remove the first i to make sting
Remove the s to make ting
Remove the g to make tin
Remove the t to make in
Remove the n to make I

stringier
Remove the r to make stingier
Remove the i to make stinger
Remove the t to make singer
Remove the r to make singe
Remove the g to make sine
Remove the e to make sin
Remove the s to make in
Remove the n to make I

strapping
Remove the s to make trapping
Remove the t to make rapping
Remove the p to make raping
Remove the r to make aping
Remove the a to make ping
Remove the g to make pin
Remove the p to make in
Remove the n to make I

Posted in Riddles

Aiden and Sofia Buying Candy

Aiden and Sofia were debating a major purchase of candy. They calculated that they could get three bags of jelly beans and two bags of chocolate for 24 cents, which was just under their limit of 25 cents. They found they could also get four bags of chocolate and two bags of jelly beans for the same 24 cents. How much did each bag of candy cost?

Jelly beans are 6 cents and chocolate is 3 cents.

Posted in Brain Teasers

A U2 Concert

U2 has a concert that starts in 17 minutes and they must all cross a bridge to get there. All four men begin on the same side of the bridge. You must help them across to the other side. It is night. There is one flashlight. A maximum of two people can cross at one time. Any party who crosses, either 1 or 2 people, must have the flashlight with them.

The flashlight must be walked back and forth. It cannot be thrown and other tricks like that are not needed to solve the problem. The solution is simply a matter of allocating resources in a certain order. Each band member walks at a different speed. A pair must walk together at the rate of the slower man’s pace:

Bono: 1 minute to cross
Edge: 2 minutes to cross
Adam: 5 minutes to cross
Larry: 10 minutes to cross

For example: if Bono and Larry walk across first, 10 minutes have elapsed when they get to the other side of the bridge. If Larry then returns with the flashlight, a total of 20 minutes have passed and you have failed the mission.

This is one of my favorite brain teasers and I want to give you the satisfaction of figuring it out on your own. If you’re having a hard time, here’s a hint: There is a valid answer that doesn’t require tricks like throwing the flashlight or shining it backwards or having some other means of moving the flashlight.

There’s an assumption people often make that keeps them from solving this. Two members cross the bridge each time, but neither one of the two who crossed necessarily need to return. Think about how that would be possible. If you’re still stuck, use objects to simulate their movements. Use whatever you have laying around – pens, paper, erasers – and move them back and forth. Good luck!

Posted in Brain Teasers

Cowboy Corral

Two cowboys live next door to each other and both have a corral for their cows in the back. One day they meet at the back of their homes, standing next to a wall dividing their corrals. The first cowboy gets to thinking and asks his neighbor for a cow so he can double his herd. The other cowboys replies, “That’s fine by me partner, cuz then we’ll have the same number of cows?” How many cows does each cowboy own?

We’ll use A to represent the first cowboy and B for the second cowboy.

A + 1 = 2A, so A = 1.
A + 1 = B – 1, so B = 3.

Posted in Brain Teasers

A Word of Weather

Find this eight-letter word.

The first four letters are a variation of the weather.
The third through seventh letters give support but also could used when someone is executed.
And the last three letters forms the name of a person.

What’s the word?

Mistaken.

Mist = Variation of weather.
Stake = a tent stake or when someone is burned at the stake.
Ken = a person’s name.

Posted in Riddles

I Turn Around Once

I turn around once,
What is out will not get in.
I turn around again.
What is in will not get out.

What am I?

A key.

Posted in Riddles
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Consecutive Christmas Caroling

My family sings Christmas carols at the hospital where my wife works.
We do this every year and since we started, have not missed a single year.
The next time we do this will be the 18th consecutive Christmas.
My 15 year old daughter has been every time.

How is this possible?

She was born in March 1999 so the first year she came was December 1999 (before her 1st birthday).
Her first time was when she was 0, second time when she was 1, third time when she was 2, etc…

Now that she is 15, she has been 16 times. Oh and of course she was also present in December 1998 in her mum’s belly, due to be born the next March.

So, a total of 17 times and next time will be the 18th.

Thanks to Michael for submitting this real-life brain teaser about his family.

Posted in Brain Teasers

Penny, Cork and A Bottle

Given a corked bottle with only a penny inside, how can you remove the penny without pulling out the cork, breaking the bottle and leaving the cork intact?

Push the cork into the bottle, then shake the penny out.

Posted in Brain Teasers