Sunday, 2 November 2014

Penny Problem

 Understand the problem


Left drawer has 64 pennies and the right one has none.


1. First Question


Can you arrange things so that one of the drawers has 48 pennies, using the following two operations:


l: If the left drawer has an even number of pennies, you may transfer half of them to the right drawer. If the left drawer has an odd number of pennies, operation l is disallowed.

r: If the right drawer has an even number of pennies, you may transfer half of them to the left drawer. If the right drawer has an odd number of pennies, operation r is disallowed. 

2. Second Question


What about arranging things so that one of the piles has other numbers in the range [0,64]

3.Third Question


What about starting with a different number of pennies in the left drawer?


Devise a plan


Work Backwards

Carry out the plan

First Question
48 - 16
32  - 32
64  - 0


Second Question/Third Question: You can still be successful.
34 - 30
60 - 4
62 - 2
63 - 1
64 - 0

Look back 


Pretty simple after using the hint of working backwords.

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