Working Backward through a List (NCTM March 2006—Cartoon Corner)
EXPLAIN YOUR ANSWERS/SHOW YOUR STEPS
1. If Lucy got Schroeder to work his way backward through the list the way
she wanted, what would he say and in what order?
2. If you start with a number, then double it, then add 5, then divide by
10, you get 10.5. Work backward to find the original number.
3. A man died and left these instructions in his will: Give ½ my estate to
my wife; 1/7 of what is left to my daughter; 2/3 of the remainder to my
pet donkey; and the rest to charity. The charity got $2000. How much
money did the man leave behind?
4. How can you solve
3x  28  17 by working backward?
5. Make up your own working-backward problem. It can be a computation
problem, a word problem, or an equation.