Solution #44: House of Cards
Note first that in all houses of cards, every level has three cards more
than the level immediately above it.
The number of cards for a 47-story house is therefore
2
+ 2 + 3
+ 2 + 3.2
+ 2 + 3.3
+ ...
+ 2 + 3.(n-1)
+ ...
+ 2 + 3.(47-1)
----------------------
47.2 + 46.47/2 x 3 = 3337
Source: Berrondom, Marie
Categories: Number sense, Arithmetic
[Top |
Problem]