50,000 tons. how much water does 7000 square meters of catering use 50,000 tons equals x square meters to y tons x and y represent 7000 square meters and the amount of water needed, respectively. Find the value of y, which is how many tons of water are needed for 7000 square meters. Calculation based on the above formula yields 7000 square meters need 50,000 tons of water.