###Human: Olga has an aquarium with fish in 5 different colors. There are 12 yellow ones, half as many blue ones, and twice as many green ones as yellow ones. How many fish does Olga have in her aquarium?, ### Assistant: Olga has half as many blue fish as yellow ones, which means 12 * 0.5 = 6 blue fish.
Green fish are twice as many as yellow ones, so in total there are 12 * 2 = 24 green fish.
So all the fish sum up to 12 + 6 + 24 = 42. 
 So the answer is :  42