Percent Increase & Decrease Game

Percent Increase & Decrease Quiz/Game
Welcome to Percent Increase & Decrease Game. This game is designed to help you master percentage-based growth and decay. Unlike simple conversions, this game asks you to apply a percentage to a base number to find a final result. The percentage given allows you to use mental math to solve. Scroll down the page for a more detailed explanation.

 

 

How to play the Percent Increase & Decrease Game

1. Choose Your Training Module
   From the main menu, you can select one of four modes:
   Practice Mode: It only asks you to find the change amount (e.g., “What is 10% of 80?”). It focuses on 10% and 25%.
   Percent Increase: You find the percentage, then add it to the original number.
   Percent Decrease: You find the percentage, then subtract it from the original number.
   Mixed Mode: It swaps between Increase and Decrease randomly.
   

2. How to Solve the Challenges
   Once you click a module, a question will appear in the green chamber.
   Identify the Base and Percent: For example, “Increase 80 by 25%."
   Find the Change: Calculate what 25% of 80 is (80 × 0.25 = 20). (or use one of the metal strategies described below)
   Apply the Change: Since it is an Increase, add that 20 back to the base (80 + 20 = 100).
   Submit: Type 100 into the box and hit Enter or click Submit Answer.
   

3. The Streak & Feedback
   For every correct answer, your Streak goes up, and the 🔥 icon grows larger.
   The Shake: If you get an answer wrong, the screen will shake, a low “thud” will play, and your streak resets to 0.
   The Answer Key: Don’t worry if you miss one—the game will display the correct answer at the bottom so you can learn from the mistake.
   

4. Tips
   To calculate faster than a calculator, use these mental shortcuts.
   

The “Power of 10” Rule
To find 10% of any number, simply move the decimal point one place to the left.
10% of 80 is 8.0
10% of 150 is 15.0
10% of 22 is 2.22

The “Half and Half” (25% and 50%)
Use division for these common benchmarks rather than multiplication.
50% (The Half): Just cut the number in half (divide by 2).
Example: 50% of 60 is 30.
25% (The Quarter): Cut the number in half, then half again (divide by 4).
Example: 25% of 80 → Half is 40 → Half again is 20.

The “Double 10” (20%)
Once you know the 10% trick, you can find 20% instantly.
Step 1: Find 10% (move the decimal).
Step 2: Double it.
Example: 20% of 70 → 10% is 7 → Double it to get 14.

4. Applying the “Change” to the Total
   The game doesn’t just ask for the percentage; it asks for the final result.
   For Percent Increase Think: “Start + Change”
   Question: Increase 40 by 25%.
   Bridge: 25% of 40 is 10.
   Action: 40 + 10 = 50.
   For Percent Decrease Think: “Start - Change”
   Question: Decrease 60 by 10%.
   Bridge: 10% of 60 is 6.
   Action: 60 - 6 = 54.
   

Percents using Mental Math

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