Question 1

How to calculate 20% of 100?

Accepted Answer

To calculate 20% of 100, multiply 100 by 0.20 (20/100). The result is 20.

Question 2

How to calculate percentage increase?

Accepted Answer

To calculate percentage increase, subtract the original value from the new value, divide by the original value, and multiply by 100. For example, if a value increases from 50 to 75, the percentage increase is ((75-50)/50) × 100 = 50%.

Question 3

How to calculate sales tax?

Accepted Answer

To calculate sales tax, multiply the price by the tax rate (as a decimal). For example, with a 7% sales tax on a $100 item, the tax would be $100 × 0.07 = $7, making the total price $107.

Question 4

How to calculate discount prices?

Accepted Answer

To calculate a discounted price, multiply the original price by the discount percentage (as a decimal), then subtract that amount from the original price. For a 25% discount on a $80 item: $80 × 0.25 = $20 (discount amount), $80 - $20 = $60 (final price).

Question 5

What is the formula for percentage?

Accepted Answer

The basic formula for percentage is (Part/Whole) × 100. For example, if 25 out of 50 students passed a test, the percentage who passed is (25/50) × 100 = 50%.

Calculation Type	Formula	Example
X% of Y	(X/100) × Y	20% of 80 = 0.2 × 80 = 16
X is what % of Y	(X/Y) × 100	15 is 30% of 50
% Change	((New-Old)/Old) × 100	75 to 100 = 33.33% increase
Add X% to Y	Y + (Y × X/100)	Add 15% to 200 = 230
Original value	Result ÷ (Percentage/100)	25 is 20% of 125

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