Nicole has 4 fish tanks. The first two tanks need 8 gallons of water each and the other two need 2 fewer gallons of water each than the first two tanks. If Nicole needs to change the water of the aquarium every week, how many gallons of water will she need in four weeks? Think carefully first, then make a decision:
The first two tanks need 8 x 2 = 16 gallons of water. The other two tanks need 8 - 2 = 6 gallons of water each. So, the two other tanks need 6 x 2 = 12 gallons of water. Nicole needs 16 + 12 = 28 gallons of water every week for her four tanks. Therefore, she needs a total of 28 x 4 = 112 gallons of water in four weeks. So, the answer is 112.