What is Percentage Decrease?

S1-SA2-0304

Grade Level:

Class 5

Maths, Finance, Economics, AI, Data Science, Statistics

Definition

What is it?

Percentage decrease tells us how much something has gone down compared to its original value, shown as a percentage. It helps us understand the proportional reduction in a quantity or price. We calculate it by finding the actual decrease, then dividing it by the original value, and finally multiplying by 100.

Simple Example

Quick Example

Imagine your favourite chai shop used to sell a cup of chai for ₹20. Now, they have a special offer, and the chai costs ₹18. The price has decreased. To find the percentage decrease, we would compare this ₹2 decrease to the original ₹20 price.

Worked Example

Step-by-Step

Let's say a cricket bat originally cost ₹1200. During a sale, its price dropped to ₹900. Let's find the percentage decrease.

Step 1: Find the actual decrease in price.
Original Price = ₹1200
New Price = ₹900
Decrease = Original Price - New Price = ₹1200 - ₹900 = ₹300

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Step 2: Divide the decrease by the original price.
Fractional Decrease = Decrease / Original Price = ₹300 / ₹1200 = 1/4

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Step 3: Convert the fraction to a percentage by multiplying by 100.
Percentage Decrease = (1/4) * 100%

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Step 4: Calculate the final percentage.
Percentage Decrease = 0.25 * 100% = 25%

The percentage decrease in the cricket bat's price is 25%.

Why It Matters

Understanding percentage decrease helps you make smart choices, like finding the best deals when shopping. It's also used by businesses to track sales, by economists to study price changes, and even in data science to analyze trends. Many jobs, from marketing to finance, use this concept daily.

Common Mistakes

MISTAKE: Dividing the decrease by the NEW value instead of the ORIGINAL value. | CORRECTION: Always divide the amount of decrease by the starting (original) value to get the correct percentage decrease.

MISTAKE: Forgetting to multiply by 100 at the end. | CORRECTION: After dividing the decrease by the original value, multiply the result by 100 to express it as a percentage.

MISTAKE: Confusing percentage decrease with percentage increase. | CORRECTION: Remember that percentage decrease specifically means the value has gone down, and you always subtract the new value from the original to find the 'decrease amount'.

Practice Questions

Try It Yourself

QUESTION: Your mobile data plan used to give you 5 GB of data. Now, due to a network issue, it's temporarily reduced to 4 GB. What is the percentage decrease in data? | ANSWER: 20%

QUESTION: A small shop's daily sales dropped from ₹8000 on Monday to ₹7200 on Tuesday. Calculate the percentage decrease in sales. | ANSWER: 10%

QUESTION: An auto-rickshaw driver's daily earnings were ₹1500. Due to heavy rain, his earnings decreased by 30% the next day. What was his earning on the rainy day, and what was the actual decrease amount? | ANSWER: Earning on rainy day: ₹1050, Actual decrease: ₹450

MCQ

Quick Quiz

A school had 500 students last year. This year, the number of students decreased to 450. What is the percentage decrease in the number of students?

10%

15%

20%

The Correct Answer Is:

The decrease is 500 - 450 = 50 students. Percentage decrease = (50 / 500) * 100% = 0.1 * 100% = 10%.

Real World Connection

In the Real World

You see percentage decrease when online shopping apps like Myntra or Amazon announce '50% off' sales during festivals like Diwali. Businesses use it to show discounts. Even financial news channels report percentage decreases in stock prices or economic growth, helping people understand market changes.

Key Vocabulary

Key Terms

PERCENTAGE: A fraction out of 100. | DECREASE: To go down in value or amount. | ORIGINAL VALUE: The starting amount or price before any change. | REDUCTION: Another word for decrease or markdown.

What's Next

What to Learn Next

Great job understanding percentage decrease! Next, you can learn about 'Percentage Increase'. It's very similar, but instead of finding how much something went down, you'll learn how to calculate how much it went up, which is also super useful in daily life!