document.write( "Question 871483: I need help with this question, thank you in advance!!! \r
\n" ); document.write( "\n" ); document.write( "A study has shown that 20% of all college textbooks cost at least $70. It is known that the standard deviation of the prices of the college textbook is $9.50. Assuming that prices of all college textbooks follows a normal distribution; find the mean price of all college textbooks. \n" ); document.write( "

Algebra.Com's Answer #525629 by ewatrrr(24785) $\"\"$ $\"About$

You can put this solution on YOUR website!


\n" );
document.write( "Hi
\n" );
document.write( "invNorm(.80) = .8416  Note:  80% cost < $70
\n" );
document.write( ".8416 = (70-m)/9.5
\n" );
document.write( "9.5(.8416) = 70 - m
\n" );
document.write( "    m = 70 - 9.5(.8416) = 70 - 7.995 = $62 \n" );
document.write( "

\n" );