Profit And Loss
Math MCQs

Question :    A shopkeeper loses 31% by selling an article for $972.90. For how much should he sell it to get a profit of 30%?

Correct Answer  1833

Solution & 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) = $972.9

And, the loss = 31%

Then, the Sale Price (SP) to earn a profit of 30% = ?

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 – 31} × 972.9

= ¹⁰⁰/₆₉ × 972.9

= ^{100 × 972.9}/₆₉

= ⁹⁷²⁹⁰/₆₉ = 1410

Thus, the Cost Price (CP) = $1410

Finding the Sale Price using the formula when the cost price and Profit percent are known

Here now, CP = $1410

And, profit = 30%

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 + 30}/₁₀₀ × 1410

= ¹³⁰/₁₀₀ × 1410

= ^{130 × 1410}/₁₀₀

= ¹⁸³³⁰⁰/₁₀₀ = 1833

Thus, Sale Price (SP) at a profit of 30% = $1833 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) = $972.9

And, the loss = 31%

Then, the Sale Price (SP) to earn a profit of 30% = ?

Let the Cost Price (CP) = m

Here given loss = 31%

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

= 31% of m

= 31% × m

= ³¹/₁₀₀ × m

⇒ loss = ^{31 m}/₁₀₀

Calculation of Cost Price (CP)

The Sale Price (SP) = Cost Price (CP) – loss

⇒ 972.9 = m – ^{31 m}/₁₀₀

⇒ 972.9 = ^{100 m – 31 m}/₁₀₀

⇒ 972.9 = ^{69 m}/₁₀₀

After cross multiplication, we get

972.9 × 100 = 69 m

⇒ 69 m = 972.9 × 100

⇒ m = ^{972.9 × 100}/₆₉

⇒ m = ⁹⁷²⁹⁰/₆₉ = 1410

⇒ m = 1410

Thus, the Cost Price (CP) = $1410

Finding the Sale Price (SP) when the Cost Price (CP) and profit percent are known

Now, here, Cost Price = 1410

And, the profit = 30%

Thus, Sale Price (SP)

= Cost Price (CP) + 30% of Cost Price (CP)

= 1410 + ³⁰/₁₀₀ × 1410

= 1410 + ^{30 × 1410}/₁₀₀

= 1410 + ⁴²³⁰⁰/₁₀₀

= 1410 + 423 = 1833

Thus, Sale Price (SP) at a profit of 30% = $1833 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) = $972.9

And, the loss = 31%

Then, the Sale Price (SP) to earn a profit of 30% = ?

Let, CP = 100

30% profit = 30% of CP

= 30% of 100 = 30

Thus, Sale Price to earn a profit of 30% = CP + 30

= 100 + 30 = 130

⇒ Sale Price to earn a profit of 30% = 130

31% loss = 31% of CP

= 31% of 100 = 31

Thus, Sale Price at a loss of 31% = CP – Loss

= 100 – 31 = 69

⇒ Sale Price at a loss of 31% = 69

∵ If the Sale Price is 69, then to earn a profit of 30% the Sale Price should be = 130

∴ If the Sale Price is 1, then to earn a profit of 30% the Sale Price should be

= ¹³⁰/₆₉

∴ If the Sale Price is 972.9, then to earn a profit of 30% the Sale Price should be

= ¹³⁰/₆₉ × 972.9

= ^{130 × 972.9}/₆₉

= ¹²⁶⁴⁷⁷/₆₉ = 1833

Thus, Sale Price to get a profit of 30% = $1833 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) = $972.9

And, the loss = 31%

Then, the Sale Price (SP) to earn a profit of 30% = ?

Here, the Sale Price at a loss of 31 = $972.9

This means 69% of the Cost Price (CP) = 972.9

Therefore, 1% of the Cost Price (CP) = ^972.9/₆₉

Therefore, 100% of the Cost Price (CP)

= ^972.9/₆₉ × 100 = 1410

Thus, the Cost Price (CP) = $1410

Now, we need to find the Sale Price at a profit of 30%

Thus, Sale Price at a profit of 30%

= 130% of the Cost Price (CP)

= 130% of 1410

= ¹³⁰/₁₀₀ × 1410 = 1833

Thus, the Cost Price at a profit of 30% = $1833 Answer

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