Melody has three dogs. Each dog eats 1/2 of a pound of dog food twice a day. If Melody bought 30 pounds of dog food, how many pounds of dog food are left after a week? Think carefully first, then make a decision:
Each dog eats 1 / 2 x 2 = 1 pound of dog food each day. So the three dogs eat a total of 1 x 3 = 3 pounds each day. That is 3 x 7 = 21 pounds in a week. Therefore, 30 - 21 = 9 pounds of food are left after a week. So, the answer is 9.