Apyramid of energy has 100 units of energy available for the first trophic level. how many units would be available for the primary consumers? how did you calculate this?

10 units

Explanation:

The typical transfer of energy from one trophic level to another is 10%. In this case, the producers are the ones in the first trophic level, so they are the ones that have 100 units of energy. The primary consumers, thus the consumers of the producers will get around 10% of the energy of the producers, meaning that they will only get 10 units of energy. The secondary consumer for example will get 10% of the energy of the primary consumer, but that means that it will get only 1% of the energy that the producers had.

This is very easy to calculate. The number of initial energy units should just be divided with 10, and that goes on for every trophic level.