Three Items for $100

Bill buys three items at the store for exactly $100. The second item costs half as much as the first item, and the third item is half as much as the second.

How much did each one cost?

First: $57.14
Second: $28.57
Third: $14.29

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ABCD equals DCBA

What 4-digit number abcd satisfies this equation?

4 × abcd = dcba

2178

4 × 2178 = 8712

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Eight Eleven Five Sequence

Which two numbers are missing and where do they go in the sequence?

8, 11, 5, 14, 1, 7, 6, 10, 13, 3, 12, 2

The missing numbers are 4 and 9. The list is sorted alphabetically by the English spelling of the numbers, so four belongs after five and nine comes after fourteen.

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Buying Chickens

You must buy 100 chickens for exactly $100, and purchase at least one chicken from each store. The first store charges 5 cents/chicken, the second charges $1/chicken and the third charges $5/chicken. How many chickens should you buy from each store?

80 from store 1 = $4
1 from store 2 = $1
19 from store 3 = $95

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What One One One Represents

What do the following numerals represent?

11111121113122223222

The number of syllables in the numbers from one to twenty.

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Two Three Ten Sequence

If:
2 3 = 10
7 2 = 63
6 5 = 66
8 4 = 96
9 7 = __

What is the missing number?

f(n, m) = (n + m) × n

e.g. f(2, 3) = (2 + 3) × 2 = 10

Hence, f(9, 7) = (9 + 7) × 9 = 144

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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

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Death By Marbles

You are a prisoner sentenced to death. The Emperor offers you a chance to live by playing a simple game. He gives you 50 black marbles, 50 white marbles and 2 empty bowls and instructs you to divide the 100 marbles into the two bowls. You can divide them however you want as long as all the marbles are in the bowls. You will be blindfolded and the bowls and marbles will be thoroughly mixed. You will then choose a single marble from one of the bowls. If the marble is white, you live. Black and you will be put to death.

How do you divide the marbles up so that you have the greatest probability of choosing a white marble?

Place one white marble in one bowl and place the rest of the marbles in the other bowl (49 whites, and 50 blacks).

This way you begin with a 50/50 chance of choosing the bowl with one white marble and living. Even if you choose the other bowl, you still have an almost 50% chance of picking one of the 49 white marbles. There are no guarantees in life, but this gives you the best change of surviving.

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Two Two Four Sequence

What number comes next?

2, 2, 4, 12, 48, ___

240. To get the number, multiply the previous number in the series by its position. 48 is in the 5th position, so 48 × 5 = 240

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A Dog Running in the Forest

How far can a dog run into the forest?

Halfway. After that it will be running out of the forest.

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