We have already learnt that ratio means comparing two quantities and about the percentage, it also come from the ratio.
As we say about the ratio about a basket has 20 mango and 80 grapes than we say 20:80 in similarly in out of 100 it's called 20% mango and 80% grapes.
Yes, Percentage means any ratio or number will be out of 100 and percentage is denoted by % symbol.
To finding the increase or decrease percentage means gain or loss, increment or decrement of the ratio, of the numbers.
Suppose ram used the unitary method. 20% increase means, Rs.100 increased to Rs. 120.
So, Rs. 34,000 will increase to?
Increased price = Rs. 120/100 x 3400
= Rs. 40,800
So, here ram has increase the percent
Discount is a reduction given on the Marked Price (MP) of the article
So, Discount = Marked price − Sale price
You can also find discount when discount % is given.
Sometimes when an article is bought, some additional expenses are made while buying or before selling it. These expenses have to be included in the cost price.
These expenses are sometimes referred to as overhead charges. These may include expenses like amount spent on repairs, labour charges, transportation etc.
Cost Price (CP) = Sale Price (SP) − Actual Price (AP)
SP > CP
Profit (P) % = P/100 x CPx
By finding the combined CP and SP to say whether there was an overall profit or loss.
Sales tax (ST) is charged by the government on the sale of an item. It is collected by the shopkeeper from the customer and given to the government. This is, therefore, always o the selling price of an item and is added to the value of the bill. There is another type of tax which is included in the prices known as Value Added Tax (VAT).
From July 1, 2017, Government of India introduced GST which stands for Goods and Services Tax which is levied on supply of goods or services or both.
Interest is the extra money paid by institutions like banks or post offices on money deposited (kept) with them. Interest is also paid by people when they borrow money. We already know how to calculate Simple Interest.
SI = P(1 + rt)
Where P is the Principal amount of money to be invested at an Interest Rate R% per period for t Number of Time Periods.
The interest paid or charged is never simple. The interest is calculated on the amount of the previous year. This is known as interest compounded or Compound Interest (C.I.).
If you might have come across statements like “one year interest for FD (fixed deposit) in the bank @ 9% per annum” or ‘Savings account with interest @ 5% per annum’.
Calculating Compound Interest
C.I. = P +SI
P= Principle
SI= Simple Interest
Finding the new way of Compound interest.
A = P (1 + 
)n
Time period and rate when interest not compounded annually.
The time period after which the interest is added each time to form a new principal is called the conversion period. When the interest is compounded half yearly, there are two conversion periods in a year each after 6 months. In such situations, the half yearly rate will be half of the annual rate.
I = P x r x 1/2/100
There are some situations where we could use the formula for calculation of amount in CI.
Here are a few.
Increase (or decrease) in population.
The growth of a bacteria if the rate of growth is known.
The value of an item, if its price increases or decreases in the intermediate years.