1

Question

A trader used to make 5% profit on an item selling at usual marked price. One day, he trebled the marked price of the item and finally offered a discount of 30%. Find the percentage profit he made on the item that day.

Open in App

Solution

The correct option is **D**

**Method 1:** Conventional approach

Cost of a tubelight = Rs. t and cost of a bulb = Rs. b

t + b = 52

Cost of bulb drops by 20% and cost of tubelight increases by 50%

Therefore, 1.5t + 0.8b = 50

Solving the two equations in 't' and 'b',

t + b = 52

1.5t + 0.8b = 50

Multiplying first equation by 4 and second equation by 5,

4t + 4b = 208

7.5t + 4b = 250

Subtracting,

3.5t = 42

Hence, t = 12

Thus, cost of a tubelight = Rs. 12

Shortcut!- Reverse Gear

Checking for option (c)

Rs.12

Cost of a tubelight = Rs. t and cost of a bulb = Rs. b

t + b = 52

Cost of bulb drops by 20% and cost of tubelight increases by 50%

Therefore, 1.5t + 0.8b = 50

Solving the two equations in 't' and 'b',

t + b = 52

1.5t + 0.8b = 50

Multiplying first equation by 4 and second equation by 5,

4t + 4b = 208

7.5t + 4b = 250

Subtracting,

3.5t = 42

Hence, t = 12

Thus, cost of a tubelight = Rs. 12

Shortcut!- Reverse Gear

Checking for option (c)

Tubelight1015Bulb42335248

From this we can deduce that the cost of the tubelight is very close to our assumption. We can also directly mark option (d) as the correct answer without verifying because with a Rs.10 tubelight we are getting the new cost as Rs.48 ; thus the cost of the tubelight has to be slightly more than Rs.10 to get the cost of the package as Rs.50 !

0

Join BYJU'S Learning Program

Join BYJU'S Learning Program