# CBSE Class 8 Maths Revision Notes Chapter 8

## CBSE Class 8 Mathematics Revision Notes Chapter 8 – Comparing Quantities

In these Class 8 Mathematics  Chapter 8 notes from the CBSE syllabus, students will learn about Comparing Quantities. In addition, in these Class 8 Mathematics  notes, from NCERT books, students will get to know the important details of the chapter that are important for their final examination. Along with Chapter 8 Mathematics Class 8 notes, Extramarks will provide students with essential questions that can be asked to prepare them quickly. Moreover, Class 8 Mathematics notes will be a student’s go-to CBSE revision notes providing all the necessary information. These notes are based on the CBSE syllabus.

These notes contain all the topics in the NCERT books concisely. These CBSE revision notes are made according to the CBSE syllabus. Download the Class 8 Mathematics Chapter 5 notes on this page to improve your exam results. Once you go through these notes, you can easily solve CBSE sample papers to test your understanding. These notes also contain CBSE extra questions that will help students test their understanding. These notes contain important questions and formulas to help students achieve better marks in their examinations.

• Ratio:
• The ratio is the terminology to compare using division.
• The ratio of quantities’ units is the same.
• Ratios have no unit.
• The equality of two ratios is called proportion. It means,

p:q is equally proportional to s:t.

That means

p:q::s:t

pq=st

• Product of extremes = Product of means
• Percentage:
• The number of people in a group of 100 is referred to as “percentage.”
• A percentage is the result of any division with a divisor of 100
• Percentage is calculated as:

Percentage=ValueTotal Value X 100

• The divisor is represented by the percent (%) symbol.
• Profit And Loss:
• Cost Price (CP):

The initial unit purchase price is called the cost price of an object.

• Selling Price (SP):

The amount a buyer pays for it is known as its selling price.

• Overhead expenses are those sustained after buying an item and are included in the cost price. These can include costs of repair, labour, transportation, and more.
• A discount is a deduction in the price of an item that has already been marked down.

Discount = Marked Price – Sale Price

The Marked price is the price tagged or listed, which is the labelled price of an item or product.

It is the price at which the product will be offered for sale to the buyer.

• When a % of discount is specified, here is how we could calculate the discounted price.

Discount = Discount % of Marked Price

However, there could be a reduction applicable to the price, and the product’s actual selling price might be lower than the marked price.

1. Marked Price > Selling Price, when the seller offers a discount.
2. Marked Price = Selling Price, when a discount is unavailable.
• Overhead expenses are expenses sustained after the purchase of an article and are included in the cost price.

• The government levies a sales tax on the sale of a product, which is then added to the total billed price.

Sales tax = Tax

• GST (Goods and Services Tax) is a tax levied for providing goods, services, or both.
• Simple Interest:

When the principal remains the same during the loan term, the interest paid is called simple interest.

SI=P X R X T100

• Compound Interest:

The interest calculated on the sum from last year’s amount is referred to as compound interest.

A = P+I

1. When Compound Interest Is charged annually, The total amount

=P 1+R2100 n

Where, P is principal, R is rate of interest and n is the time period.

1. When Interest Is compounded half-yearly, the amount

=P 1+R21002n

R2 is the half-yearly rate and 2n = No. of ‘half-years’

We calculate the interest twice if the interest is compounded half-yearly. As an outcome, the time period is doubled, and the rate is divided in half.

• Applications of Compound Interest:

In daily life, compound interest applies to determine the following segments:

1. Growth of population (or decrease).
2. Growth of bacteria if the growth rate is known.
3. The object value if its price hikes or falls over multiple years.

### 1. Calculate the ratio of the following: (a) The cycle speed is 15 km per hour to the speed of a scooter, which is 30 km per hour. (b) 5 m to 10 km (c) 50 paise to ₹ 5

(a) Speed of cycle : Speed of Scooter = 15 km per hour : 30 km per hour

= 1530=12

Hence, the ratio = 1 : 2

(b) 5 m to 10 km

= 5 m : 10 × 1000 m [∵ 1 km = 1000 m]

= 5 m : 10000 m

= 1 : 2000

Hence, the ratio = 1 : 2000

(c) 50 paise to ₹ 5

= 50 paise : 5 × 100 paise

= 50 paise : 500 paise

ratio = 1 : 10

### 3. 72% of 25 students are good at maths. How many of them are not good?

No. of students who are good in Maths= 72% of 25

No. of students who are not good in Maths= 25 – 18 = 7

### 4. A soccer team won 10 matches out of the total number of matches they played. If their win percentage was 40, how many matches did they play?

The soccer team won 40 matches out of 100 matches

A match was won out of 10040 matches

The team won 10 matches out of 10040 × 10 = 25 matches

Hence, the total number of matches the team played = 25.

### 5. If Anjali had ₹ 600 left after spending 75% of her money, what amount did she have in the beginning?

Let the money with Anjali had be ₹ 100

Money spent by her = 75% of 100

= 75100× 100 = ₹ 75

Money remaining with her = ₹ 100 – ₹ 75 = ₹ 25

₹ 25 is remaining from of ₹ 100

₹ 1 is left with her out of ₹ 10025

₹ 600 will be left out of ₹ 10025 × 600 = ₹ 2400

Hence, the amount she had in the beginning = ₹ 2400.