How much pure alcohol should be added to 400ml of a 15% solution to make the strength of solution 28%?
Options.
A) 100 ml  B) 60 ml  C) 120 ml  D) 140 ml  E) 150 ml
we can also go by answer choices   Tke 100 ml for eg   400 (old)+100 (new concentr)ml     500*28/100= 
<gadget id="calculator">  500*28/100</gadget>
<output>140</output>
140 ml (40ml is de old concentration +100 ml (newly added)   Answer 140 ml
<result>D</result>
How much pure alcohol should be added to 400ml of a 15% solution to make the strength of solution 28%?