Through exercise, Rod went from 8 lb above his "ideal" body weight to 9 lb below it. How many pounds did Rod lose?

Question

The book says the answer is 17 lb. I can't figure out how this can be. I see the problem as 8 + (-9) = -1. I don't see how both numbers are to be added. HELP!!!!

Answer 1

The words "went from" mean there is a beginning value (+8) and an ending value (-9).  [note above is + and below is -]

 

The change is the ending value minus the beginning value.  So, (-9) - 8 = -17.  The "-" means that the change was a loss.

 

Suppose Rod went from 8 lb above "ideal" body weight to 10 lb above "ideal" body weight because he ate pizza during the Super Bowl.  How much weight did Rod gain?    10 - 8 = +2  [after - before; + means gain].

 

But, a player in the Super Bowl went from 5 lbs above his "ideal" body weight just before the game to 3 lbs below his "ideal" body weight just after the game, how many pounds did he lose (note: -)?