Question:
A shopkeeper gets a loss of 10% by selling an article for $324. For how much should he sell it to get a profit of 9%?
Correct Answer
392.4
Solution And Explanation
Strategy to solve the question
Step (1) Calculate the cost price at given loss percent and the sale price.
Step (2) After gettting the cost price find the sale price at given profit percent.
Solution
Method (1) Formula Method
Finding the Sale Price to earn a profit using formula when the Sale Price at a loss is given
Given, the sale price (SP) = $324
And, the loss = 10%
Then, the Sale Price (SP) to earn a profit of 9% = ?
Formula to find the cost price when the sale price and loss percent are known
Cost Price (CP) = 100/100 – gain% × SP
Thus, the Cost Price (CP)
= 100/100 – 10 × 324
= 100/90 × 324
= 100 × 324/90
= 32400/90 = 360
Thus, the Cost Price (CP) = $360
Finding the Sale Price using the formula when the cost price and Profit percent are known
Here now, CP = $360
And, profit = 9%
Thus Sale Price (SP) = ?
Formula to find the Sale Price (SP) when the cost price (CP) and profit percent are known
Sale Price (SP) = 100 + gain%/100 × Cost Price (CP)
Thus, the Sale Price (SP)
= 100 + 9/100 × 360
= 109/100 × 360
= 109 × 360/100
= 39240/100 = 392.4
Thus, Sale Price (SP) at a profit of 9% = $392.4 Answer
Method (2) Algebraic Method
Finding the Sale Price (SP) to earn the given profit using the Algebraic Method when the Sale Pric (SP) at a loss percent is given
Given, the sale price (SP) = $324
And, the loss = 10%
Then, the Sale Price (SP) to earn a profit of 9% = ?
Let the Cost Price (CP) = m
Here given loss = 10%
Calculation of loss
loss is calculated on cost price (CP)
Formula to find the loss = loss% of CP
Thus, loss on the cost price of m
= 10% of m
= 10% × m
= 10/100 × m
⇒ loss = 10 m/100
Calculation of Cost Price (CP)
The Sale Price (SP) = Cost Price (CP) – loss
⇒ 324 = m – 10 m/100
⇒ 324 = 100 m – 10 m/100
⇒ 324 = 90 m/100
After cross multiplication, we get
324 × 100 = 90 m
⇒ 90 m = 324 × 100
⇒ m = 324 × 100/90
⇒ m = 32400/90 = 360
⇒ m = 360
Thus, the Cost Price (CP) = $360
Finding the Sale Price (SP) when the Cost Price (CP) and profit percent are known
Now, here, Cost Price = 360
And, the profit = 9%
Thus, Sale Price (SP)
= Cost Price (CP) + 9% of Cost Price (CP)
= 360 + 9/100 × 360
= 360 + 9 × 360/100
= 360 + 3240/100
= 360 + 32.4 = 392.4
Thus, Sale Price (SP) at a profit of 9% = $392.4 Answer
Method (3) Unitary Method
Finding the Sale Price (SP) to earn a given profit when the Sale price (SP) at a loss is given
Given, the sale price (SP) = $324
And, the loss = 10%
Then, the Sale Price (SP) to earn a profit of 9% = ?
Let, CP = 100
9% profit = 9% of CP
= 9% of 100 = 9
Thus, Sale Price to earn a profit of 9% = CP + 9
= 100 + 9 = 109
⇒ Sale Price to earn a profit of 9% = 109
10% loss = 10% of CP
= 10% of 100 = 10
Thus, Sale Price at a loss of 10% = CP – Loss
= 100 – 10 = 90
⇒ Sale Price at a loss of 10% = 90
∵ If the Sale Price is 90, then to earn a profit of 9% the Sale Price should be = 109
∴ If the Sale Price is 1, then to earn a profit of 9% the Sale Price should be
= 109/90
∴ If the Sale Price is 324, then to earn a profit of 9% the Sale Price should be
= 109/90 × 324
= 109 × 324/90
= 35316/90 = 392.4
Thus, Sale Price to get a profit of 9% = $392.4 Answer
Method (4) Shortcut Method
Shortcut Method to find the Sale Price at a given profit when Sale Price at a loss is given
Given, the sale price (SP) = $324
And, the loss = 10%
Then, the Sale Price (SP) to earn a profit of 9% = ?
Here, the Sale Price at a loss of 10 = $324
This means 90% of the Cost Price (CP) = 324
Therefore, 1% of the Cost Price (CP) = 324/90
Therefore, 100% of the Cost Price (CP)
= 324/90 × 100 = 360
Thus, the Cost Price (CP) = $360
Now, we need to find the Sale Price at a profit of 9%
Thus, Sale Price at a profit of 9%
= 109% of the Cost Price (CP)
= 109% of 360
= 109/100 × 360 = 392.4
Thus, the Cost Price at a profit of 9% = $392.4 Answer
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