Planet fourfi resides in 4-dimensional space and thus the currency used by its residents are 3-dimensional objects. The rupee notes are cubical in shape while their coins are spherical. However the coin minting machinery lays out some stipulations on the size of the coins.

The diameter of the coins should be at least 64mm and not exceed 512mm.
Given a coin, the diameter of the next larger coin is at least 50% greater.
The diameter of the coin must always be an integer.
You are asked to design a set of coins of different diameters with these requirements and your goal is to design as many coins as possible. How many coins can you design?
8 5 6 9

• ans is 6
  
  this is a series where t(n+1)=t(n)*1.5
  64,96,144,216,324,486
  
• 14 years agoHelpfull: Yes(11) No(1)