Question

what is the cost price of an item if the selling price is rs 21 and profit is 5%​

Answer 1

Given :

Selling price = ₹21

Profit% = 5%

To find : the Cost price.

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Method 1 :

Formula to use :

$cp = \dfrac{100}{100 + profit\%} \times sp$

$cp = \dfrac{100}{100 + 5} \times 21$

$cp = \dfrac{100}{105} \times 21$

by reducing to the lowest terms we get :

cp = ₹20

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Method 2 :

We know that,

$sp = cp + profit$

$profit = \dfrac{profit\%}{cp} \times 100$

let cp be x.

$21 = x + ( \dfrac{5}{100} \times x)$

$21 = x + \dfrac{x}{20}$

$21 = \dfrac{20x + x}{20}$

$21 \times 20 = 21x$

$\dfrac{21 \times 20}{21} = x$

$20 = x$

Therefore cp = ₹20

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You can also use to find sp formula when cp is given. Assuming cp to be a variable and substituting the other values

hope it helps!

have a great day!