If 18 is 15 percent of 30 percent of a certain number , what is the number? Choose one: A) 9 B) 36 C) 40 D) 81 E) 400
The math involved in this question can be 'set up' (and dealt with) in a variety of ways.   Here, if you're going to take a calculation-based approach, converting the percents to fractions would likely help you speed up (and avoid the last bit of math).   We're told that 18 is 15 percent of 30 percent of a certain number. We're asked for that number.   18 = (.15)(.3)(X)   18 = (3/20)(3/10)(X)   18 = (9/200)(X)   Since 9/200 is a relatively small fraction (it's far less than 10%), we know that 18 is LESS than 10% of X. Based on the given answer choices, there's only one number that is LARGE enough to fit that description....   Final Answer:   400
<result>E</result>
If 18 is 15 percent of 30 percent of a certain number , what is the number?