A pharmacist needs to strengthen a 10% alcohol solution to one of 20% alcohol.How much pure alcohol should be added to 400ml of 10% solution?
Let x ml of pure alcohol be added to 400ml of 10% solution to convert, it into 20% alcohol.
In 10% alcohol,pure alcohol in 400ml=400×10100=40ml
To be added in the solution of 400ml=xml
In 20% alcohol,pure alcohol in 400+xml=(400+x)×20100
⇒40+x=(400+x)×20100
⇒40+x=(400+x)5
⇒200+5x=400+x
⇒5x−x=400−200
⇒4x=200
⇒x=2004=50ml
Pure alcohol to be added is 50ml