The Smart family could paint 110 square feet per hour.
Step-by-step explanation:
Given that while remodeling their living room, the Smart family decided to repaint the walls, and they estimated that they could repaint 55 square feet every half-hour, to determine how many square feet can they paint per hour the following calculation must be performed:
1/2 = 0.5
0.5 = 55
1 = X
55 / 0.5 = X
110 = X
Therefore, the Smart family could paint 110 square feet per hour.