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Riya sat down for a 3-hour study block and spent 45 minutes of it on mathematics. What percent of the block went to mathematics?

Class 8Comparing QuantitiesComparing Quantities
  • A15%
  • B45%
  • C75%
  • D25%

Step-by-Step Solution

Both quantities must be in the same unit: 3 hours = 180 minutes. Percent = %. Trap: dividing 45 by 3 without converting hours to minutes gives 15%; 75% is the part she did NOT spend on mathematics.
Answer: D) 25%

Key idea: Discount

A discount is a reduction off the **marked price** (MP), not the cost price. The selling price (SP) is what the customer actually pays.

**SP = MP − Discount**
**Discount % = (Discount / MP) × 100**

Example: shirt MP ₹800, discount 25%. Discount amount = 25% of 800 = 200. SP = 800 − 200 = 600.

Note: discount % is calculated on MP. Profit/loss % (Class 7) is on CP. Don't mix them up.

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