document.write( "Question 795106: Your textbook says that the focal length f of a lens is given by the lensmaker's formula 1/f=0.6(1/r1+1/r2) where r1 and r2 are the radii of the two circular surfaces. If those radii are 4 and 6 respectively, find f. \r \n" );
document.write( "\n" );
document.write( "A. 3/25 \r \n" );
document.write( "\n" );
document.write( "B. 4 \r \n" );
document.write( "\n" );
document.write( "C. 16/67 \r \n" );
document.write( "\n" );
document.write( "D. 1/4 \n" );
document.write( " \n" );
document.write( "
![\"\"](\"/images/stars/iconNewId_16x16.gif\")
