A sells an article to $ \mathrm{B} $ at a profit of $ 20 \% $. B sells it to $ C $ at a profit of $ 4 \% . $ What does it cost $ A $ if $ C $ has paid $ Rs. 624 ? $

Given :

A sells an article to B at 20% profit.

B sells it to C at 4 % profit.

C paid 624₹.

To Find : 

Cost price at which A bought ?

Solution :

Lets take Cost  price of B = Rs. B

Cost price of A = Rs. A

C paid to B Rs. 624

So, B sells for Rs. 624 at 4% profit.

104% of B = Rs. 624

$\frac{104}{100} \times B = Rs. 624$

B = Rs. $\frac{624\times100}{104}$

B  = Rs. $6\times100 = 600$

B = Rs. 600

So, B buys it at Rs. 600 from A.

Selling price of A =Rs. 600

A sells it at 20% profit

120% of A = Rs. 600

$\frac{120}{100} \times A = Rs. 600$

A = Rs. $\frac{600\times100}{120}$

A = Rs. $5\times100 = 500$

A  = Rs. 500

Cost price at which A bought = Rs. 500.