If we are not allowed to use a weighing machine then what are our options? Well, there aren’t very many.
It helps to think of natural things of which we already know the properties of. Let’s think of water – that’s something natural that has a lot of measurable properties.
What could we do with water?
Well, we do know that one of the properties of water is that it weighs 1 kg. per liter, or 8.34 lbs per gallon. How can we use this knowledge to our advantage to solve this problem?
Put the elephant in a full tank of water
What if we put the elephant on a big raft inside a full tank of water?
What we could do then is measure the volume of water that’s displaced from the tank and that would give us a great approximation of the weight of the elephant.
So, let’s suppose that 7500 liters (or about 1,900 gallons) of water is displaced. Because 1 liter of water weighs 1 kilogram then that means the elephant weighs about 7500 kilograms. Because there are 2.2 pounds in 1 kilogram, this is about 16,500 pounds.