Question

On selling 17 balls at Rs. 720, there is a loss equal to the cost price of 5 balls. The cost price of a ball is:
A. Rs. 45
B. Rs. 50
C. Rs. 60
D. Rs. 55

Answer 1

Hint: In this question, cost price is unknown and the loss is given in terms of cost price. So here we will first assume that the cost price is Rs.x. After this, we will calculate the loss in terms of cost price. Finally use the given information in question to form the equation.

Complete step-by-step answer:
In the question, we have:
Selling price(S.P.) of 17 balls = Rs. 720
Loss = cost price (C.P.) of 5 balls.
And we have to find the cost price.
First of all assume that the cost price of a ball = Rs. x.
$\therefore $ Cost price of 17 balls = Rs.17x
Now it is given that loss = cost price of 5 balls
$\therefore $ Loss = Rs.5x

We know that the relation between selling price, cost price and loss is given by:
Cost price = Selling price + Loss (1)
Putting the values in above equation, we get:
17x = 720 + 5x
$ \Rightarrow $ 17x – 5x = 720
$ \Rightarrow $ 12x = 720
$ \Rightarrow $ x = $\dfrac{{720}}{{12}} = 60$
Therefore, the cost price of a ball = Rs. 60
So, option C is correct.

Note: In solving the problems related to topic profit and loss, you have to remember two basic formulas: Cost price = selling price + Loss and Cost price = selling price – profit. In most of the questions any two data are given and another has to be calculated or the value of one data is given and loss/profit is given in terms of another unknown value. In this case proceed in the way that we have done here.