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A merchant purchases a cloth at a rate of Rs. 100100 per meter and receives 5 cm5 \mathrm{~cm} length of cloth free for every 100 cm100 \mathrm{~cm} length of cloth purchased by him. He sells the same cloth at a rate of Rs. 110110 per meter but cheats his customers by giving 95 cm95 \mathrm{~cm} length of cloth for every 100 cm100 \mathrm{~cm} length of cloth purchased by the customers. If the merchant provides a 5%5 \% discount, the resulting profit earned by him is

Solution

✅ Correct Option: 1

The merchant has three sources of advantage:

Getting extra cloth when buying (5 cm free per 100 cm), giving less cloth when selling (95 cm instead of 100 cm), and charging premium price (Rs. 110 vs Rs. 100 cost).

Even after giving a 5% discount, let's see the final profit.


What we pay: Rs. 100 for 100 cm of cloth

What we actually get: 100 cm + 5 cm free = 105 cm

Effective cost per cm: Rs. 100 ÷ 105 cm = Rs. 100105\dfrac{100}{105} per cm


Listed selling price: Rs. 110 per meter (100 cm)

What customer actually gets: Only 95 cm (instead of 100 cm)

Effective revenue per cm sold: Rs. 110 ÷ 95 cm = Rs. 11095\dfrac{110}{95} per cm

After 5% discount: Rs. 11095×0.95=104.595\dfrac{110}{95} \times 0.95 = \dfrac{104.5}{95} per cm


For the 105 cm of cloth we actually have:

Total Cost: Rs. 100 (what we paid)

Total Revenue: 105×104.595=115.5105 \times \dfrac{104.5}{95} = 115.5 cm

Profit: Rs. 115.5 - Rs. 100 = Rs. 15.5

Profit Percentage: 15.5100×100=15.5%\dfrac{15.5}{100} \times 100 = 15.5\%


The reference solution uses a clever multiplier approach:

Selling Price = 110×(1+120)×(1+119)×0.95110 \times \left(1 + \dfrac{1}{20}\right) \times \left(1 + \dfrac{1}{19}\right) \times 0.95

Where:

(1+120)\left(1 + \dfrac{1}{20}\right) accounts for getting 5 cm free per 100 cm

(1+119)\left(1 + \dfrac{1}{19}\right) accounts for giving 95 cm instead of 100 cm

0.950.95 accounts for the 5% discount

Calculation:

110×2120×2019×95100=110×21×20×9520×19×100=115.5110 \times \dfrac{21}{20} \times \dfrac{20}{19} \times \dfrac{95}{100} = 110 \times \dfrac{21 \times 20 \times 95}{20 \times 19 \times 100} = 115.5

Final Answer: The profit percentage is 15.5%


Key Insight: Even after giving a 5% discount, we still make a healthy profit due to the combined effect of getting extra cloth when buying and giving less cloth when selling. This is a common type of profit calculation problem where multiple factors work together.

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