We all love a good puzzle, and if you’re like me, calling it “unsolvable” only makes you more determined to figure it out. That said, these are actually really hard. Like, really hard.

Like, if you figure them out without looking, you’re way smarter than me. Give it a shot!

## #1. A Locked Door

You have 100 bags of coins each with 100 coins, but only one of these bags as gold coins. The gold coin weighs 1.01 ounce and the other coins weigh 1 ounce. You also have a scale, but can only use it once. How can you identify the bag of gold coins?

## #2. The Burning Ropes

You can given two ropes and a lighter. Each of the two ropes has the following property: if you light one end of the rope, it will take exactly one hour to burn to the other end. It doesn’t necessarily burn at a uniform rate. How can you measure a period of 45 minutes?

## #3. Glass Half Full

You are in an empty room with a transparent glass of water. The glass is a right cylinder and appears to be half full. How can you accurately figure out whether the glass is half full, more than half full, or less than half full? You have no rulers or writing utensils.

## #4. Cork, Bottle, Coin

You put a coin in an empty bottle and insert a cork in the bottle’s opening. How can you remove the coin without taking out the cork or breaking the bottle?

## #5. Global Trek

How many places are there on earth where one could walk one mile south, then one mile west, then one mile north and end up in the same spot? The earth is a solid, smooth sphere.

Answers on the next page!

## #1. Do some maths.

Give the bags numbers from 0-99, then take 0 coins from the bag number 0, 1 coin from the bag number 1, 2 coins from the bag number 2, and so on until we take 99 coins from the bag number 99. Gather all the coins we have taken together and put them on the scale. Then subtract 5050 (the weight of 1+2+3…etc.) from the total weight. If you have .01 left, then the first bag has the gold. If you get .66 left, then the 66th bag has the gold.

## #2. Light both ends of rope A and one end of rope B.

After 30 minutes, rope A will be completely burned up and there will be thirty minutes of rope B left. Light the other end of rope B; it will burn up in 15 minutes. Total time elapsed since starting the ropes on fire: 45 minutes.

## #3. Tilt the glass.

Carefully tilt the cylindrical glass until the surface of water just touches the upper brim of the glass. Make sure no water spills out of it. Now check whether the surface of water also touches the brim of the bottom surface of the glass. If it does, then the glass is exactly half full. If the surface of water is just above the bottom brim, then the glass is more than half empty and otherwise it is less than half empty.

## #4. Push the cork into the bottle.

You’ll be able to shake out the coin.

## #5. An infinite number.

The obvious answer is the North Pole, but actually there are an infinite number of answers because near the poles, directions get pretty fuzzy. Check out a much more detailed answer HERE.

h/t: Buzzfeed

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