Assume that the grasshopper in the food pyramid above must eat half its body weight in grass each day. If an average-size grasshopper weighs 2 grams, and 1 blade of grass weighs 0.1grams (one tenth of a gram), how many blades of grass does the grasshopper need to eat each day?

The first thing we need to know is how much grass the grasshopper needs to eat.
 We have:
 "must eat half its body weight in grass each day":
 (2 grams) * (1/2) = 1 gram
 Then,
 "1 blade of grass weighs 0.1grams"
 Then the amount you need to eat is given by:
 N = (1) / (0.1)
 N = 10 blades of grass
 Answer:
 the grasshopper needs to eat 10 blades of grass each day