Question 960804
<pre>            |  no. of bags | % as  | no. of bags of
            |  of pre-mix  |decimal|  pure cement
------------|--------------|-------|---------------
   4% cement|      x       | 0.04  |    0.04x
------------|--------------|-------|---------------
11.6% cement|     10       |0.116  |  0.116(10)
------------|--------------|-------|---------------
   8% cement|    x+10      | .08   | 0.08(x+10)

0.04x + 0.116(10) = 0.08(x+10)

Solve to get answer

Edwin</pre>