What is a Decrease Percentage?

S1-SA2-0353

Grade Level:

Class 3

All STEM domains, Finance, Economics, Data Science, AI, Physics, Chemistry

Definition

What is it?

A decrease percentage tells us how much something has gone down compared to its original amount, shown as a part of 100. It helps us understand the reduction in a value relative to its starting point. For example, if a price drops, the decrease percentage shows how much cheaper it became.

Simple Example

Quick Example

Imagine your favourite chai shop sold 100 cups of chai yesterday. Today, they only sold 80 cups. The number of cups sold has decreased. To find the decrease percentage, we compare this drop (20 cups) to the original 100 cups.

Worked Example

Step-by-Step

Let's say a mobile phone's price was ₹10,000. During a sale, its price dropped to ₹8,000. What is the decrease percentage?

1. Find the actual decrease in price: Original Price - New Price = ₹10,000 - ₹8,000 = ₹2,000.
---2. Write the decrease as a fraction of the original price: Decrease / Original Price = ₹2,000 / ₹10,000.
---3. Simplify the fraction: 2,000 / 10,000 = 2 / 10 = 1 / 5.
---4. Convert the fraction to a percentage by multiplying by 100: (1 / 5) * 100%.
---5. Calculate: 100 / 5 = 20%.

So, the mobile phone's price decreased by 20%.

Why It Matters

Understanding decrease percentage is super useful! Businesses use it to show discounts, economists track how prices change, and data scientists use it to see trends. It's key for making smart financial decisions and understanding data in many fields like science and technology.

Common Mistakes

MISTAKE: Calculating the percentage decrease based on the new (smaller) value instead of the original value. | CORRECTION: Always divide the amount of decrease by the ORIGINAL starting value, not the final value.

MISTAKE: Forgetting to multiply by 100 at the end to convert the fraction or decimal into a percentage. | CORRECTION: After finding the ratio of decrease to original, always multiply by 100% to express it as a percentage.

MISTAKE: Confusing decrease percentage with increase percentage. | CORRECTION: Remember, decrease percentage means the value went down. The calculation always involves the 'amount of decrease' over the 'original amount'.

Practice Questions

Try It Yourself

QUESTION: A cricket player's score dropped from 50 runs in one match to 40 runs in the next. What is the percentage decrease in his score? | ANSWER: 20%

QUESTION: The number of students attending a science club went from 80 to 60. Find the percentage decrease in attendance. | ANSWER: 25%

QUESTION: A shopkeeper bought a toy for ₹500 and planned to sell it for ₹600. However, due to low demand, he sold it for ₹450. What is the percentage decrease from his *planned* selling price to his *actual* selling price? | ANSWER: 25%

MCQ

Quick Quiz

A packet of biscuits originally cost ₹20. Now it costs ₹15. What is the percentage decrease in its price?

0.05

0.2

0.25

0.3333

The Correct Answer Is:

The decrease is ₹20 - ₹15 = ₹5. The original price is ₹20. So, (5/20) * 100% = (1/4) * 100% = 25%.

Real World Connection

In the Real World

When you see '50% off' sales during Diwali or festival season at your local clothing store or on apps like Myntra, they are using decrease percentages! Even when petrol prices go down, news channels report the percentage decrease, helping everyone understand the impact on their daily budget.

Key Vocabulary

Key Terms

PERCENTAGE: A part of a whole expressed as a fraction of 100 | DECREASE: To become smaller in amount or value | ORIGINAL VALUE: The starting amount or price before any change | REDUCTION: The act of making something smaller or less | RATIO: A comparison of two numbers by division

What's Next

What to Learn Next

Great job understanding decrease percentage! Next, you can explore 'What is an Increase Percentage?' It's the opposite concept and uses similar steps. After that, you'll be ready to tackle more complex percentage problems, like profit and loss!