A rectangular tank weighs 310kg, when it is half full of water and 450kg, when it is three quarters full of water. What is the weight of the tank when it is empty?

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Answer 1

Weight when half full = 310kg
Weight when three quarters full = 450kg

Weight of water when half full = 310kg
Weight of water when three quarters full = 450kg - 310kg = 140kg

Weight of tank when empty = 310kg - 140kg = 170kg