2010 AMC 10B Problems/Problem 12
The minimum possible value occurs when $20%$ (Error compiling LaTeX. Unknown error_msg) of the students who originally answered "No." answer "Yes." In this case, 
The maximum possible value occurs when $30%$ (Error compiling LaTeX. Unknown error_msg) of the students who originally answered "Yes." answer "No." and the $50%$ (Error compiling LaTeX. Unknown error_msg) of the students who originally answered "No." answer "Yes." In this case, 
Subtract 
to obtain an answer of 
