Riddle:

If you're 8 feet away from a door and with each move you advance half the distance to the door. How many moves will it take to reach the door?

Infinity! Technically you will never reach the door, as you can only move half the distance, no matter how small.

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Riddle:

What two whole, positive numbers that have a one-digit answer when multiplied and a two-digit answer when added?

1 and 9.

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Riddle:

I am four times as old as my daughter. In 20 years time I shall be twice as old as her.

How old are we now?

I am 40 and my daughter is 10.

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Riddle:

How many times can you subtract the number 5 from 25?

Once, because after you subtract it's not 25 anymore.

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Riddle:

How do you make the number 7 an even number without addition, subtraction, multiplication or division?

Drop the "S".

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Riddle:

Can you write down eight eights so that they add up to one thousand?

888 + 88 + 8 + 8 + 8 = 1000.

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Riddle:

One is to three as three is to five and five is to four and four is the magic number.

What is the pattern?

One has three letters in the word three has five letters in it five has four letters and four has four letters in it (if you try more numbers they will always come back to the number four: so four is the magic number)

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Riddle:

What number is that, which, added separately to 100 and 164, shall make them perfect squares?

125.

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Riddle:

2, 3, 5, 9, 17, _ What is the next number in the sequence?

33. The pattern:  Double the previous number and subtract 1.

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Riddle:

An item is made from lead blanks in a lathe shop. Each blank suffices for 1 item. Lead shavings accumulated for making 6 items can be melted and made into a blank. How many items can be made from 36 blanks?