Word Problems with Start Unknown - Up to 20
🎬 Rewind the clock! In these problems, we know what happened at the end, but we don't know what happened at the very beginning.
Do this: Read the concept below, then try the quiz or activity.
Concept
These are the ultimate backwards puzzles! We have to act like detectives looking at clues and figuring out how the story started.
🎯 The "Start Unknown" Puzzle: Story: "Some frogs were on a log. 4 more frogs jumped on. Now there are 13 frogs on the log. How many frogs were on the log at the start?" * Start: ??? (We don't know!) * Change: + 4 frogs jumped on. * Result: 13 frogs total.
Equation: ??? + 4 = 13. How do we solve this? Work BACKWARDS! If we know the answer is 13, and we got there by adding 4, we need to do the OPPOSITE. We need to subtract 4 from 13! * 13 - 4 = 9. * So, there were 9 frogs at the start!
Try it
Rewind the story and find the start!
Instructions: Work backward to find the mysterious starting number.
Problem 1: Some kids were on the bus. 6 kids got off. Now there are 8 kids left. How many kids were on the bus at the start? * Equation: ___ - 6 = 8 * Work backward: Do the opposite! Add 8 + 6! * Answer: ___ kids at the start.
Problem 2: You had some stickers. Your teacher gave you 7 more. Now you have 15 stickers. How many did you start with? * Equation: ___ + 7 = 15 * Work backward: 15 - 7 = ? * Answer: ___ stickers at the start.
Problem 3: You bought a book. You gave the cashier $20. The cashier gave you $3 back in change. How much did the book cost? * Answer: ___ dollars