Give the step-by-step reasoning process and then the final answer. Wallace's water heater is twice the size of Catherine's water heater. If the capacity of Wallace's water heater is 40 gallons and it's 3/4 full, calculate the total number of gallons of water they both have if Catherine's water heater is also full with water to 3/4 of its capacity.
When 3 / 4 full of water, Wallace's water heater has 3 / 4 * 40 = 30 gallons of water. Catherine's water heater capacity is 40 / 2 = 20 gallons. When 3 / 4 full, Catherine's water heater has 3 / 4 * 20 = 15 gallons of water. Together, when 3 / 4 full with water, Wallace's and Catherine's water heaters hold 15 + 30 = 45 gallons of water.
The final answer: 45.