If the grasshoppers in a certain area receive 500 million joules of chemical energy from the plants they eat in one day, what is a reasonable estimate of the amount of chemical energy the frogs in the same area will get from their food?

I had this same exact question. It seems as though each trophic level decreases by 10% each time it goes up; like how producers is 100% then primary consumers are 10% and then the secondary consumers are 1%. So that's where the grass and other organisms come into play. Because the grasshoppers are receiving 500 joules in chemical energy, I would assume that means that the frogs are getting about 50% of that energy because of the trophic level. That is just what I think.