Solution to puzzle 20

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The question was

A magic rectangular belt always shrinks its length to 1/2 and width to 1/3 whenever its owner wishes something. After three such wishes, its surface is now 4 cm2. What was the original length, if the original width was 9 cm?

Solution : 96cm


  1. If the original width was 9cm, width after first wish, it is 3cm.
    •  After second wish, the width is 1cm. 
    • After third wish the width is 1/3cm
  2. If the area is 4cm2, then the length after 3 wishes is 4/(1/3 ) = 4X3 = 12.
  3. After second wish, the length is double of 12 = 24
  4. After first wish, the length is double of 24 = 48.
  5. The original length of the belt is double of 48 = 96


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