Question 9902
NOTE:  See last paragraph first.  It's probably easier!!  R^2


I think it might be a good idea to set up a ratio, using this information: If 20% (i.e., .20) combines, then 80% (i.e., .80) does NOT comine.  Let x = amount that combines, which is what you need to find.


{{{ (combined)/(not_combined)}}}:  {{{.20/.80 = x/740}}}


Remember {{{a/b=c/d}}} means that {{{a*d=b*c}}}, so
{{{.20/.80 = x/740 }}}


This reduces to {{{1/4 = x/740}}} which means that 
{{{4x = 740}}} 
{{{x=740/4}}}
{{{x= 185}}} kg 


Now that I think about this, there is probably an easier way to do this, like just realizing that for every part that combines there are 4 parts that do not combine.  Therefore, the amount that combines is 1/4 of the amount that does not combine, and 1/4 of 740 = 185 kg.  That would have been a lot easier.  Oh well.  Too late now.


R^2 at SCC