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An item with a cost price of Rs. 1650 is sold at a certain discount on a fixed marked price to earn a profit of 20% on the cost price. If the discount was doubled, the profit would have been Rs. 110. The rate of discount, in percentage, at which the profit percentage would be equal to the rate of discount, is nearest to

Solution

✅ Correct Option: 3

Selling price at the original discount:

SP=1650×1.2=1980SP = 1650 \times 1.2 = 1980

Since this SP comes from applying a discount dd on the Marked Price:

MP(1−d)=1980⋯(1)MP(1 - d) = 1980 \quad \cdots (1)


When the discount is doubled, profit =110= 110:

SP2=1650+110=1760SP_2 = 1650 + 110 = 1760

MP(1−2d)=1760⋯(2)MP(1 - 2d) = 1760 \quad \cdots (2)


Subtracting equation (2)(2) from (1)(1):

MP(1−d)−MP(1−2d)=1980−1760MP(1 - d) - MP(1 - 2d) = 1980 - 1760

MP−MPd−MP+2MPd=220MP - MPd - MP + 2MPd = 220

MPd=220MPd = 220

Substituting back into (1)(1):

MP−220=1980MP - 220 = 1980

MP=2200MP = 2200

d=2202200=0.1=10%d = \dfrac{220}{2200} = 0.1 = 10\%


A special discount rate r%r\% is needed such that the profit percentage on CP also equals rr.

When discount =r%= r\%, the SP becomes:

SP=2200(1−r100)SP = 2200\left(1 - \dfrac{r}{100}\right)

Setting profit %\% on CP equal to rr:

2200(1−r100)−16501650×100=r\dfrac{2200\left(1 - \dfrac{r}{100}\right) - 1650}{1650} \times 100 = r

550−22r1650×100=r\dfrac{550 - 22r}{1650} \times 100 = r

55000−2200r=1650r55000 - 2200r = 1650r

55000=3850r55000 = 3850r

r=550003850≈14.29%r = \dfrac{55000}{3850} \approx 14.29\%

This is nearest to 1414.

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