Class 8 · Chapter 8

Comparing Quantities

Percentages, profit/loss, discount, compound interest.

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Tip: open the NCERT PDF for the original chapter text alongside the notes here.

Detailed theory

% change

= \dfrac{\text{new} - \text{old}}{\text{old}} \times 100

. Positive: increase; negative: decrease.

Key concepts & formulas

\text{Profit\%} = \dfrac{\text{Profit}}{\text{CP}} \times 100

SI = \dfrac{P\cdot R\cdot T}{100}

A = P\left(1 + \dfrac{R}{100}\right)^n

for compound interest.

Discount is calculated on Marked Price.

Successive discount: apply one after the other.