Question

In the following food chain, 100 J of energy is available to the lion. How much energy was available to the producer?

Plants → Deer → Lion

Answer 1

Plants → Deer → Lion
It is given that 100 J of energy is available to lion. 
Let the amount of enrgy available to deer be x Joules.
According to 10% law, only 10% energy from deer must have been transfered to lion so, energy available to deer can be calculated as,

⇒ 10% of x = 100 J

⇒ `10/100xxx=100 J`

`therefore x=100J`

∴ Energy available to the deer = 1000 J
Let the energy available to the producer be y J.
By problem,
⇒ 10% of y = 1000 J

⇒ `10/100xxy =1000J`

⇒ y = 10,000 J.

So we have found that energy available to producer is 10,000J.