Question

25)Example 20 A manufacturer has 600 litres of a 12% solution of acid. How many litres

of a 30% acid solution must be added to it so that acid content in the resulting mixture

will be more than 15% but less than 18%?

Answer 1

Solution Let x litres of 30%o acid solution is required to be added. Then

Total mixture = (x + 600) litres

Therefore 30%x+ 12% of 600 > 15% of (x+ 600)

And 30% x + 12% of 600 < 18% of (x + 600).  

or30x/100+12/100(600)>15/100(x+600)

And 30x/100+12/100(600)<18/100(x+600)

or 30x + 7200 > 15x+ 9000

and 30x + 7200 < 18x+ 10800

Or 15x> 1800 and 12x < 3600

Or X> 120 and x < 300,

ie.

120