Aasifbhai bought a refrigerator at Rs 10,000. After some time he sold it to his friend at Rs 9000, then how much profit or loss does he make?
(a) 10% loss
(a) 10% loss
(a) 20% loss
(d) 30% loss

Hint: In order to solve this problem, we need to find whether the person has made a profit or suffered a loss. When selling price is greater than cost price then the person has made a profit and when cost price greater than selling price than the person has suffered a loss. The formula for loss is $\text{Loss = cost price - selling price}$ . The formula for profit made is $\text{Profit = selling price - cost price}$.
The formula for the profit percentage is $\text{profit percantage = }\dfrac{\text{profit}}{\text{cost price}}\times 100$ . The formula for loss percentage is $\text{loss percantage = }\dfrac{\text{loss}}{\text{cost price}}\times 100$

Complete step-by-step answer:
We can interpret from the question that the customer bought a refrigerator at Rs 10,000.
Therefore, the cost price of the refrigerator is 10,000.
It is told in the question that he sold the refrigerator at Rs 9000.
Therefore, the selling price of the refrigerator is Rs 9000.
When the cost price is higher than the selling price then there is a loss to the person.
When the selling price is higher than the cost price then there is a profit to the person.
In this problem we can clearly say that the cost price is greater than the selling price, therefore, there is a loss to aasifbhai.
We need to find the loss. For that, we need to take the difference between cost price and selling price.
Therefore, loss = cost price – selling price.
 Substituting, the values we get,
Loss = 10,000 – 9,000 = Rs 1000.
Now we need to find the loss percentage,
We need to keep in mind that whether it’s a loss percentage or profit percentage, it is always compared with respect with cost price
Therefore, $\text{Loss percantage = }\dfrac{\text{loss}}{\text{Cost price}}\times 100$,
Substituting the values, we get,
$\text{Loss percentage}=\dfrac{1,000}{10,000}\times 100=10%$
Therefore, aasifbhai suffered a loss of 10%.
Hence, the correct option is (a).

Note: Just by comparing the cost price and selling price we can eliminate the options. In this, we can see that the cost price is greater than the selling price therefore, there is a definite loss. Therefore, option (b) is eliminated. Also, we need to keep in mind that whether it is a loss or profit in case of percentage loss and profit both are compared with respect to cost price.