How much pure alcohol should be added to 400ml of a 15% solution to make the strength of solution 25%?  Choose one
A) 100 ml  B) 60 ml  C) 125 ml  D) 130 ml  E) 150 ml
we can also go by answer choices   Tke 100 ml for eg   400 (old)+100 (new concentr)ml     500*25/100= 
<gadget id="calculator">  500*25/100</gadget>
<output>125</output>
125 ml (25ml is de old concentration +100 ml (newly added)   Answer 125 ml
<result>C</result>
How much pure alcohol should be added to 400ml of a 15% solution to make the strength of solution 25%?