Question

A manufaturer 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

hęłłø hęřę įß ÿøûř æñßwęř ⤵⤵

Let x litres of 30% 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)
or 30x100+12100(600)>15100(x+600)and
 30x100+12100(600)<18100(x+600)or 
30x+7200>15x+9000
and
 30 x +7200<18x+10800
or
 15x>1800 and 12x<3600or x >120 
and x<300

So 120<x<300


Thus the number of liter of 30% solution of acid will have to be more than 120 litres but less than 300 litres......