posted by msj .
Without his glasses, Isaac can see objects clearly only if they are less than 4.2 m from his eyes. What focal length glasses worn 2.2 cm from his eyes will allow Isaac to see distant objects clearly?
Our book says to convert the cm to m and subtract the two numbers-
4.2 - 0.022 = 4.178m. We submit our answers on-line though, and this answer was incorrect. What am I doing wrong?
the answer should be negative