Question

How many units of a 10% solution are needed to prepare 500 units of a 2% solution?

Answer 1

First find how many units of solution there is:

500* 2% = 500(.02) = 10 units

You need 10 units of solution in 'x' units of a 10% solution.

x*10% = 0.1x = 10 units   ----->  x = 10/0.1 = 100

100 units are needed