### Brain Teasers

# The 199th Gas Station

The 199th Gas Station is very large. It has ten rows of 10 double-sided pairs of pumps. The pump I am at is the only non-working pump.

How many working gas pumps are there at the 199th Gas Station?

How many working gas pumps are there at the 199th Gas Station?

### Answer

399 pumps.10(rows) X 10 X 2 X 2 - 1 = 399

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## Comments

I disagree. There should only be 199 pumps working, each with 2 sides. And if you are counting the number of people that can pump gas at a single time, then 1 pump out of order would mean that 398 people can pump gas.

Sorry. I agree with the given answer. It says double sided "pairs". In other words each pump set has a super and a regular pump on each side, making 4 to the set. 10 to a row makes 40 and ten rows make 400. It says nothing about how many people can pump gas (and anyway I could fill my motor mower can with regular while you were filling your motorbike with super at the same pair of pumps.

I got 199. If there are ten rows of ten double-sided gas pumps, there will be 100 in all when you multiply them together. Then, you multiply it times two since all the gas pumps are double-sided. It then leaves you with the number 200. So there are 200 gas pumps. But one doesn't work so you subtract 1 from the 200 which gives you 199!

DOUBLE-SIDED PAIRS... I agree with the answer. The above means at every "station" there is 4 pumps... 10 rows of 10 stations..

I also agree with the answer. One of the main giveaways that it is not 199 is the fact that the name is 199th Gas Station. (It would just be too easy if that were the case.) Just a thought.

Mixee.

Mixee.

thank you for your comments. I originally submitted this with bad wording and it made no sense, but now i think it is still a little confusing but that is what makes some people get the wrong answer.

A pair of anything is 2. It does not matter whether the thing is one-sided, two-sided, or one million-sided. It does not matter whether it is a pump or a polygon.

A double-sided pump is one double-sided pump. If you have in mind two pumps back to back, call them that, TWO pumps back to back, not A (which means ONE) double-sided pump.

A double-sided pump is one double-sided pump. If you have in mind two pumps back to back, call them that, TWO pumps back to back, not A (which means ONE) double-sided pump.

Is a double-sided pump = 2 pumps?

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