6 liters of milk and water mixture has 75% milk in it. How much milk should be added to the mixture to make it 90% pure?

In what ratio must water be added to spirit to gain 25% by selling it at cost price?

A shopkeeper has 50 kgs of rice. He sells a part of it at 20% profit and the rest at 40% profit. If he gains 25% on the whole, find the quantity of each part.

The average monthly salary of employees, consisting of officers and workers, of an organisation is Rs. 3000. The average salary of an officer is Rs. 10,000 while that of a worker is Rs. 2000 per month. If there are total 400 employees in the organisation, find the number of officers and workers separately.

If 4 kg of an alloy made of 1/4th iron and rest is mixed with 6 kg of another alloy made of 2/3rd iron and rest tin, find the ratio of iron to tin in the resultant mixture.

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