There are weights that no conventional scale can measure. Sometimes the solution is not to look for a bigger scale, but to think differently.
The elephant and the boat
Riddle statement
A rajah wants to find out how much his elephant weighs, but he does not have a scale capable of supporting it.
He does have the following:
- a boat that perfectly supports the weight of the elephant,
- a pier,
- and as many 1 kilo stones as you need.
How can you find out the weight of the elephant using only those things?
Show solution
Solution
The elephant is placed in the boat and allowed to sink to its natural level. The corresponding waterline is then marked on the hull or next to the pier.
Then the elephant is taken out and 1 kilo stones are added until the boat sinks again to exactly the same mark.
At that moment, the total weight of the stones is equal to the weight of the elephant.