Tom fills a 250 pound sandbag 80% full.  But the filling material he is using is 40% heavier than sand.  How much does the bag weigh?
The bag full of sand would weigh 250 * .8 = 
<gadget id="calculator">250*.8</gadget>
<output>200</output>
200 pounds.
The filling material would make it 200 * .4 = 
<gadget id="calculator">200*.4</gadget>
<output>80</output>
80 pounds heavier.
So it weighs 200 + 80 = 
<gadget id="calculator">200+80</gadget>
<output>280</output>
280 pounds.

<result>280</result>