The Bus Driver

You are the bus driver. At your first stop, you pick up 29 people. On your second stop, 18 of those 29 people get off, and at the same time 10 new passengers arrive. At your next stop, 3 of those 10 passengers get off, and 13 new passengers come on. On your fourth stop 4 of the remaining 10 passengers get off, 6 of those new 13 passengers get off as well, then 17 new passengers get on. What is the color of the bus driver’s eyes?

The eye color of the reader of this problem. The first sentence is the key: “You are the bus driver”.

Posted in Brain Teasers

Bank Wait Times

Suppose a small bank has one teller and customer transactions take 10 minutes on average. With 5.8 customers arriving per hour, what is the expected wait time? What would it be if you added a second teller?

With one teller, customers will wait nearly five hours on average. But adding a second teller makes the wait go down to 3 minutes.

Thanks to John D. Cook for this one.

Posted in Brain Teasers

Take It And You Will Lose

Take it and you will lose or gain more than all others.

Risk.

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

Posted in Riddles

I Look Like What I Represent

I am one of very few, perhaps the only one, to look like what I represent. What am I?

The word ‘bed’, which looks like an actual bed. The ‘b’ is the headboard, the ‘e’ is the mattress and the ‘d’ is the foot board.

If you know of another word that looks like the object it represents, add it in the comments.

Posted in Riddles

Going the Wrong Way on a One-Way Street

Noreen doesn’t have a driver’s license and goes the wrong way on a one-way street, then turns left at a corner with a “No left turns” sign. A policeman sees her but does nothing. Why?

She was walking.

Posted in Brain Teasers

Remove Six Letters

Remove six letters from this sequence to reveal a familiar English word.

BSAINXLEATNTEARS

The familiar English word that remains is BANANA after removing the phrase “SIX LETTERS”.

Posted in Riddles

What is the First Number of the Sequence?

If a number in a numeric sequence is 17 and the second number is 3, what is the first number?

I hesitated to add this because it’s poorly worded, ambiguous and the answer could be almost anything. I prefer teasers with a single answer, but there you go.

If you came up with a different answer and can explain how you did it, don’t think you’re wrong. It’s probably just as valid. Feel free to share yours in the comments.

My answer for the first number is 2.

Here’s how I got it.

The generic rule for a number in the sequence is: 2^(n – 1) + 1, where n is the position in the sequence.

Note: The teaser doesn’t specify the position of 17. In this case, it’s fifth.

Position 1: (so n = 1) is 2^(1 – 1) + 1 = 2

Position 2: 2^(2 – 1) + 1 = 3

Position 3: 2^(3 – 1) + 1 = 5

Position 4: 2^(4 – 1) + 1 = 9

Position 5: 2^(5 – 1) + 1 = 17

For the curious, the next 5 numbers of the sequence would be:

Position 6: 2^(6 – 1) + 1 = 33

Position 7: 2^(7 – 1) + 1 = 65

Position 8: 2^(8 – 1) + 1 = 129

Position 9: 2^(9 – 1) + 1 = 257

Position 10: 2^(10 – 1) + 1 = 513

Posted in Brain Teasers

Kevlar, Fire Escapes and Wipers, Oh My!

What do computer compilers, kevlar, fire escapes and windshield wipers all have in common?

They were all invented by women.

A variation of this brain teaser includes laser printers (they were invented by Gary Starkweather) and bulletproof vests (invented by Casimir Zeglen using silk, though modern vests use Kevlar, so it’s halfway right).

Posted in Brain Teasers

How to Escape?

A man is trapped in a room with only two possible exits. Through the first door is a room with an enormous magnifying glass causing the blazing hot sun to instantly burn anything that enters. Through the second door there is a fire-breathing dragon. How does the man escape?

Leave through the first door at night when the sun is down.

Posted in Brain Teasers

Frederick’s Epitaph

Frederick died after a long and productive life of 87 years, but this epitaph was written on his headstone:

Frederick lived a good long life,
He loved his children and his wife,

He was honest, kind and deserved nothing but praise,
Even if he only had twenty-one birthdays.

How is this possible?

He was born on February 29th in a leap year. Consequently, in his 87 years, he only witnessed twenty-one of his actual birthdays. The other years there was no February 29th.

Posted in Brain Teasers