###Human: In one of the building blocks at Oakland High there are 5 classes. Each class uses 2 whiteboards each and each whiteboard needs about 20ml of ink for a day's use. If ink costs 50 cents per ml, how much (in dollars) would it cost to use the boards for one day?, ### Assistant: Each ml of ink costs 50 cents so 20 ml costs 20*50 = 1000 cents
There are 2 whiteboards in each class so each class needs 2*1000 cents = 2000 cents
There are five classes in the block so they all need 5*1*2000 cents = 10000 cents
100 cents make a dollar so 10000 cents make 10000/100 = $100 
 So the answer is :  100