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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.

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The Sheep’s Will

A farmer dies leaving a will dividing his flock of nineteen sheep with the following ratios:

Half to his oldest son, a quarter to the middle son and one fifth to his youngest son.

Without cutting any sheep up, how did the executor of the will fulfill the farmer’s wishes?

The executor went to the neighbouring farm and asked to borrow a sheep for a few minutes. Then he returned to the sons and said, “Half of the (now) twenty sheep is 10. A quarter of the twenty sheep is 5. A fifth of the twenty sheep is 4. 10 + 5 + 4 = 19. Then the executor took the borrowed 20th sheep back to the neighbour.

Thanks to Annette for sending this in.

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Ages Of Myself and My Brother

My current age, is the age of my 14 year-old brother plus one third of my age. How old will I be when my brother is twice his current age?

I will be 35. I am currently 21.

x = my current age

x = 14 + x/3
3x = 42 + x
2x = 42
x = 21 (so 14 years later, I'll be 35)
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Word Value Of 52

If every letter of the alphabet is worth its numerical value (A=1, B=2, C=3), what’s a common 11-letter word whose letter values total only 52?


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He And She Both Have One Each

He and she both have one each, but every person has two. A citizen has three and a human being has four. A personality has five and an inhabitant of earth has six. What are they?


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Augustus’ Candy

Augustus loves candy and much to his delight, his three favorites are on sale. One each of gum, chocolate and caramel cost 40 cents. A caramel is over three times the price of gum. Six gums are worth more than chocolate. A caramel plus two gums cost less than chocolate. What is the price of each candy?

Gum = 4 cents
Chocolate = 23 cents
Caramel = 13 cents

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Maya’s Stamps Errand

Maya’s mother asked her to buy some stamps. The available stamps were 3 cents, 9 cents, 11 cents, 17 cents and 21 cents. Her mother asked her to buy eight each of three stamps and nine of each of the remaining two stamps. Unfortunately, Maya forgot which stamps she was supposed to buy eight and nine of. Luckily, her mother had given her $5, the exact amount required to buy the stamps. Which stamps did she buy?

Eight of the 11 cent, 17 cent and 21 cent stamps and nine of the 3 cent and 9 cent stamps.

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Alphabetized Letters

What well known series can these alphabetized letters be rearranged to form?


Alpha, beta, gamma, delta

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Square Root Equations

Arrange the digits 1 through 9 into an equation so that the first number is the square root of the second number. (Two possible variations)

5672 = 321,489


8542 = 729,316

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Letter Missing From a Series

What letter is missing from this series?

The letter E. The series contains all of the letters that rhyme with bee (apologies to any English speakers who pronounce Z as zed instead of zee if this confused you).

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