In a grass-deer-tiger food chain, the tiger is left with 10J of energy. What is the energy available at the grass level?

1000 J

The tiger is left with 10J of energy in a grass → deer → tiger food chain. The energy available grass level is 100 J.

According to 10% law in the following food chain grasses → deer → tiger

if tiger have 10 J of energy then deer will have 10 time of this and grasses will have 10 times of deer, i.e. 1000 J