Question

(ii) Find the value of (625) x (625)
6. Apharmacist needs to strengthen a 10% alcohol solution to one of 20%
alcohol. How much pure alcohol should be added to 400ml of 10%
solution​

Answer 1

Answer:

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= 400×10/100 = 40ml.

To be added in the solution of 400ml=xml

In 20% alcohol,pure alcohol in 400+xml=

(400+x)×20/100

⇒40+x= (400+x)×20/100

⇒40+x= (400+x)/5.

⇒200+5x=400+x

⇒5x−x=400−200

⇒4x=200

⇒x= 200/40

=50ml

Pure alcohol to be added is 50 ml