John want to buy a $100 Trouser at the store, but he think it’s too expensive. Finally, it goes on sale for $50. What is the percent decrease?
Answers:  A) 20%  B) 30%  C) 50%  D) 70%  E) 80%
The is always the difference between our starting and ending points. In this case, it’s 100 – 50 = 50. The “original” is our starting point; in this case, it’s 100. (50/100)*100 = (0.5)*100= 
<gadget id="calculator">(0.5)*100</gadget>
<output>50</output>
50%.   50%
<result>C</result>
John want to buy a $100 Trouser at the store, but he think it’s too expensive. Finally, it goes on sale for $50. What is the percent decrease?