Concept 2 of 5
Work Backwards
Today's big idea
Run the story backwards
Undo each step with its opposite.
How it works
👀 What's going on?
You know how a story ends and want to know how it began. Run the film in reverse: whatever was done going forward, you undo coming back.
💡 Here's the trick
Look at the problem above. It tells you the end and asks for the start. To travel back, do the opposite of each step: undo adding by subtracting, undo taking away by adding, undo doubling by halving.
- 1.Find the ending number and the step that was done.
- 2.Do the opposite step to that ending number.
- 3.That takes you back to the starting number.
✍️ Try it
I gave away 5 sweets and had 8 left. How many did I start with? Giving away was taking off 5, so undo it by adding: 8 + 5 = 13 sweets.
⚠️ Watch out
Use the opposite operation. If the story took some away, you add them back — subtracting again would send you further from the start.
See it in action
⚡ Time to play!
Start from the end and undo each step to find the beginning.
WORK BACKWARDS · ROUND 1 OF 3
I gave away 5 sweets and had 8 left. How many sweets did I start with?
What number did we start with?
Quick check
✅ VERIFICATION
A number with 7 added to it becomes 15. What was the number?
⚡ Finish the activity above first to answer.
Keep going!
Up next: Counting the Ways
Be orderly so you miss none.