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A rectangular water tank is filled to a depth of $$70$$cm. It contains $$1050$$ litres of water. Some water is taken out of the tank. The water level drops by $$25$$cm. How much water is left in the tank? 
Overseas Competition->Knowledge Point->Calculation Modules->Ratios and Proportions
$$1050\times \frac {70-25}{70} = 675$$ 