<PRE><B>Question 408875</B>
  &lt;pre&gt;&lt;font size = 3 color = &quot;indigo&quot;&gt;&lt;b&gt;
Hi
Let x represent paint needed to paint a wall 5 meters by 20 meters (100m^2
Question Sets Up a Proportion: 1 gallon of paint will cover 40 square meters
 {{{ 1/40 = x/100}}}   |cross multiplying to solve for x
    40x = 100
      x = 2.5 gal, paint needed to paint a wall 100 m^2

CHECKING our Answer***
1/40 = .025 = 2.5/100 </PRE>