Profit, Loss & Discount
The most practical chapter. Master the 'Ratio Method' for Profit%, the 'MP-CP Relation' for Discounts, and the 'Dishonest Dealer' concepts.
Expert Answer & Key Takeaways
The most practical chapter. Master the 'Ratio Method' for Profit%, the 'MP-CP Relation' for Discounts, and the 'Dishonest Dealer' concepts.
1. The Golden Ratio (CP:SP)
Avoid formulas like . Use Ratios.
- 20% Profit: 1/5 → CP=5, SP=6.
- 20% Loss: 1/5 → CP=5, SP=4.
- Profit on SP: If 20% on SP, 1/5 → SP=5, Profit=1 &implies; CP=4. Actual P% = 14 = 25%.
Example:
Q: Profit is 25% of Selling Price. Find actual Profit %.
Solution: . SP=4, P=1 → CP=3.
Actual % = 13 = 33.33%.
Actual % = 13 = 33.33%.
2. The MP-CP Relationship (Master Formula)
Direct relation between CP, MP, Profit%, and Discount%.
- Formula: CPMP = 100 - D%100 + P%.
- Use this when Discount and Profit are given to find MP or CP directly.
Example:
Q: Discount 10%, Profit 20%. If CP=900, find MP.
Solution: CPMP = 90120 = 34.
. .
. .
3. Dishonest Shopkeeper (Weight Cheating)
Profit comes from using less weight.
- Formula: True WeightFalse Weight = 100+P%100±x%.
- Logic: If he uses 900g for 1kg, he sells 900g but charges for 1000g. Profit = 100g on 900g CP.
Example:
Q: Uses 800g instead of 1kg. Sells at CP. Find Profit %.
Solution: Error = 200g. Base (False Weight) = 800g.
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4. Buy X Get Y Free
Effective Discount calculation.
- Rule: Free items are the Discount. Total items (Paid + Free) are the MP base.
- Discount % = FreeTotal × 100.
Example:
Q: Buy 3 Get 2 Free. Discount %?
Solution: Free = 2. Total = 5.
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5. Successive Discounts
Net price after multiple discounts.
- Formula: (Note the signs: ).
- Ratio: If 10% and 10% off: . Net 19% off.
Example:
Q: Two successive discounts of 20% and 10%.
Solution: Ratio: and .
. Drop 14.
. Or .
. Drop 14.
. Or .
7. The Two Articles Case
Common Scenario: Two items sold at same Price.
- Case A: Same CP. x% Gain, x% Loss → No Profit No Loss.
- Case B: Same SP. x% Gain, x% Loss → Always Loss of x²100 %.
Example:
Q: Sold two cars at 1 Lakh each. One 20% profit, other 20% loss.
Solution: Same SP. Loss = 20²100 = 4%.
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