Work Backwards
📋 What it is
When a problem gives the END result and asks for the start, reverse each step (undo the operations).
🗣️ Coach says
Some problems tell you the ending and ask for the beginning: “after spending half then $5, she has $10.” Work BACKWARDS — undo each step in reverse (add the $5 back, then double). Reversing is often far easier than guessing.
🧠 Memory hook
Given the end, reverse the steps — undo each operation backwards.
😂 Giggle
What did the carry digit say when it moved to the next column?
"Excuse me, coming through!"
😲 Whoa!
Working backwards is how you solve a maze fastest (start from the exit) and how detectives reconstruct events — reversing from the known end beats guessing forward.
✅ Quick check: She spent half her money, then $5, and has $10 left. How much did she start with? (Work backwards.)
Say your answer out loud first — then reveal.
$30 — reverse: $10 + $5 = $15 (before the $5), then ×2 = $30 (before spending half).
Undoing each step in reverse order recovers the starting amount.
🧪 Try it! (2 minutes)
Think of a number, double it, add 4. Tell a friend the result and have them work BACKWARDS to your number.
🔎 How did you work this?