Arpit sold a watch at a …

Let Cost price of watch be Rs.100

Then Selling price of watch for Arpit = 100 + 5 = Rs.105

Now, SP for Arpit = CP for Mohit.

Mohit sold watch at a gain of 4%, Then,

Selling price of watch for Mohit = 105 + 4% of 105 = 105 + 4.20 = Rs.109.20

Now, Selling price of watch for Mohit = CP of watch for Rohit.

Therefore,

Since Rohit paid Rs,109.20, when CP = Rs.100

Therefore, Rohit paid Rs.1, when CP  = 100/109.20

Therefore, Rohit paid Rs.91, when CP = 100/109.20 x 91 = Rs.83.33

The cost price of watch was Rs.83.33.

Let's Arpit paid Rs. x/- for the watch which will be the CP. Arpit's SP will be Mohit's CP as Mohit bought it from Arpit. In the same way, Rohit bought it from Mohit so Mohit's SP will be Rohit's CP.

=> Mohit's CP = x * 105/100 = 1.05x

Mohit further sold it to Rohit => Rohit's CP = 1.05x * 104/100 = 1.0920 x/-

=> 91 = 1.0920 x

x = 91/1.0920 = 83.33/- (Answer)

Ans. Let Cost Price of Arpit Watch = y 

Gain % = 5%

Selling Price for Arpit = \({y \times 105 \over 100 } = {21y\over 20}\)

Selling Price for Arpit is  Cost price for Mohit  = \(21y\over 20 \)

Gain % = 4 %

Selling Price For Mohit = \({21y\over 20} \times {104\over 100} = {21y\times 26 \over 20 \times 25} = {546y\over 500}\)

Selling price For Mohit is Cost price for Rohit, So

=> \({546y\over 500} =91\)

=> \(y = {250\over 3} = 83{1\over 3}\)

Cost Price of Arpit Watch = \(Rs. \space 83{1\over 3}\)