Question

In a 30 litre mixture of milk and water, there is 90% milk. What amount of water should be mixed in the mixture so that milk content became 80%

Answer 1

30 litre mixture of milk and water 
90% of mix is milk =30*90/100=27 litre milk and 3 litre water 
when the percent of milk become 80% i.e.,30*80/100=24 litre milk 
⇒amnt of water that must be added to make 80%milk is 6 litre