<PRE><B>Question 384479</B>
800 grams = 20% its strenth.. 

So lets start with that.

if 800 grams is 20% we need to add enough to make it 50% it original strenth. 

10% more 400 grams 
20% more 800 grams 
= 1200 = 30% add 20% it would be 2000 grams . 

100% strenth in grams with the bases being 20% is 800 so that is 1/5 original strenth.   5 times 800 grams would be 4000 grams 50% of that would be 2000 grams    

So 30% is need to make 50% it would equal= 1200 grams of dye to be added. </PRE>