Question 1207766
Fairly common two part mixture problem  Sand is the filler.  Concentration can emphasize the cement.


Maybe but often not necessary, try this:
<pre>
                   FRACTION      AMOUNT        AMT. Only Cement

The Bag             0.25          20           0.25*20

Pure Cement        1.00           x          (1)(x)

TOTAL             9.40          x+20          x+(0.25)(20)
</pre>
Equation to form should be obvious.

{{{(x+(0.25)(20))/(x+20)=0.40}}}

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