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

Always Coming But Never Arrives

What is always coming but never arrives?

Tomorrow.

Posted in Riddles

If I Can I Can

If I can, I can,
If I can’t, I freeze.

What am I?

Someone preserving food. The two most common ways of preserving food are canning and freezing. So when you preserve food, if you can can it, you do, otherwise you freeze it.

Posted in Riddles

Thirty White Horses On A Red Hill

Thirty white horses on a red hill,
first champ, then stamp, and then stand still

Your teeth.

Posted in Riddles

Stand Take Mine

What does this sentence represent?

Stand   Take  Mine  Taking
  I     You    To     My

I understand you undertake to undermine my undertaking.

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The Peace Maker Weapon

What weapon is also a peace maker?

Note: Think homonyms

A knife. It turns things into pieces.

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Grow In Trees and Have No Teeth

I grow in trees, eat living things but have no teeth and give birth to something that looks nothing like me. What am I?

A bird. They are hatched and raised in trees (nests), don’t have teeth in the traditional meaning of teeth and they lay eggs, which look nothing like a bird.

A butterfly / caterpillar could also work.

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How Old is Lilly?

Two days ago Lilly was 7 years old. Next year she will turn 10. How can this be?

Her birthday is December 31st. Today is January 1st so she was 7 two days ago, and turned 7 last year. Now she’s 8 and will turn 9 this year. And next year she’ll turn 10.

For example, if today is 01 Jan 2015:

30 Dec 2014 = age 7 (two days ago)
01 Jan 2015 = age 8 (today, she turned 8 on 31 Dec 2014, which was last year)
31 Dec 2015 = age 9 (her birthday this year)
31 Dec 2016 = age 10 (her birthday next year)

Posted in Brain Teasers

The Old Gray Surgeon

A man and his son had a terrible car accident and were rushed to the hospital. The man died on the way, but the son was still barely alive. When they arrived, an old gray surgeon was called in to operate. Upon seeing the young boy, the surgeon said, “I can’t operate – this is my son.”

How is this possible?

The surgeon was the boy’s mother.

Posted in Brain Teasers

Five Letters Sound Like Six When Pronounced

What five-letter word sounds like six letters when pronounced?

Cello. The pronunciation of c is ‘ch’, making it sound like the word has 6 letters.

Posted in Riddles