There is a beautiful garden surrounded with water on three sides and only one road leading to it. This garden has thousands of coconut trees. Anyone can visit to pick coconuts.

The coconuts can be taken in boxes only. Each box can carry 20 coconuts.You can take as many boxes as you like for free but there are ten toll barriers on the road. Each toll booth collects tax in the form of … you guessed it: coconuts. The number of coconuts taken is equal to the number of boxes. For example if you are carrying 50 boxes of coconut you have to pay 50 coconuts at each barrier.

If you took 10 boxes filled with coconuts from garden, tell me how many coconuts would you have remaining after crossing all ten toll booths?

120 I guess.

Close, but no cigar!

Try again.

100

Nope, keep trying.

Wouldn’t it be twenty?

But then (I started to work this out, but then ended up just getting very confuzzled), for every twenty coconuts you lose, don’t you lose one box? So, at the first two toll booths you cross, you’d be paying ten coconuts, but at the eighth, if you’ve lost a box, you’d only pay nine. But then, when it’s the sixth booth, you’d be going into your eighth box…so would they charge you nine coconuts, or eight?

Ugh, my brain hurts!

Am I overthinking this?

P.S.: how could you carry 120 coconuts? Aren’t coconuts pretty heavy? :D

Nope, it’s more than twenty. Keep trying.

116

1 10

2 10

3 9

4 9

5 9

6 8

7 8

8 7

9 7

10 7

200-84 = 116