Percentage - Formula Guide
Type 1 - X% of Y (most common):
Result = Y x (X ÷ 100)
Example: 18% of ₹1,200 = 1200 x 0.18 = ₹216
Type 2 - X is what % of Y:
Result = (X ÷ Y) x 100
Example: 30 is what % of 200? = (30÷200)x100 = 15%
Type 3 - Percentage change from X to Y:
Result = ((Y − X) ÷ X) x 100
Example: Price went from ₹80 to ₹100:
((100−80) ÷ 80) x 100 = +25% increase
Type 4 - Apply % change to a number:
Increase: Result = X x (1 + Y÷100)
Decrease: Result = X x (1 − Y÷100)
Example: ₹500 after 20% increase = 500 x 1.20 = ₹600
Common Percentage Uses in India
GST calculation: Find 18% GST on ₹850 → Type 1: 18% of 850 = ₹153 GST, total = ₹1,003
Salary hike: Salary is ₹45,000. Got 15% hike → Type 4: ₹45,000 + 15% = ₹51,750
Discount: ₹1,200 shirt at 30% off → Type 4: ₹1,200 − 30% = ₹840
Exam marks: Scored 432 out of 600 → Type 2: 432 is what % of 600? = 72%
