In what ratio should Darjeeling Tea costing Rs. 400 per kg be mixed with Assam Tea costing Rs. 300 per kg. So that by selling the mixture at Rs. 408 per kg, there is a gain of 20%?
A mixture contains acid and water in the ratio of 7 : 3. If 4 litres of water is added to it, then the ratio of acid and water becomes 7 : 4. What is the quantity (in litres) of acid in the mixture?
The difference between simple and compound interests compounded annually on a certain sum of money for 2 years at 4% per annum is Rs 8. The sum is ______.
Two trains are moving in opposite directions with the same speed. If the length of each train is 120 metres and they cross each other in 12 seconds, then what is the speed (in km/hr) of each train?