Maths Chapter 07: Comparing Quantities

Class 08 Maths NCERT

We know, ratio means comparing two quantities. A basket has two types of fruits, say, 20 apples and 5 oranges. Then, the ratio of the number of oranges to the number of apples = 5 : 20. The comparison can be done by using fractions as, 5/20 = 1/4 The number of oranges is 1/4 th the number of apples. In terms of ratio, this is 1 : 4, read as, "1 is to 4"

Number of apples to number of oranges = 20/5 = 4/1 which means, the number of apples is 4 times the number of oranges. This comparison can also be done using percentages.

Since contains only apples and oranges, So, percentage of apples + percentage of oranges = 100

or percentage of apples + 20 = 100

or percentage of apples = 100 - 20 = 80

Thus the basket has 20% oranges and 80% apples.

Discount is a reduction given on marked price.

Discount = Marked Price - Sale Price.

Discount can be calculated when discount percentage is given.

Discount = Discount % of Marked Price

Additional expenses made after buying an article are included in the cost price and are known as overhead expenses. 

CP = Buying price + Overhead expenses

Sales tax is charged on the sale of an item by the government and is added to the Bill Amount.

Sales tax = Tax% of Bill Amount

GST stands for Goods and Services Tax and is levied on supply of goods or services or both.

Compound interest is the interest calculated on the previous year’s amount (A = P + I).