Riley, why is the product rule so much harder than the sum rule? {{CMD_7}} Ever since 2nd grade, I've known that multiplication is {{CMD_8}}harder{{CMD_9}} than addition. {{CMD_10}} I know! I was reading somewhere that a slide-rule somehow turns ``multiplication into addition.'' {{CMD_11}} Wow! I wonder how that works? {{CMD_12}} I {{CMD_13}}think{{CMD_14}} it has something to do with logs? {{CMD_15}} What? How does this work? {{CMD_16}}