​The cost price of 120 g of rice is the same as the selling price of 150 g of it. The percentage loss is:​

Correct option is B

Given:

The cost price (C.P.) of 120 g of rice is equal to the selling price (S.P.) of 150 g of rice.

Formula Used:

​$$\text{Percentage Loss} = \frac{\text{Loss}}{\text{Cost Price}} \times 100$$​​

Solution:

Let the C.P. of 120 g = S.P. of 150 g = x.

C.P. of 1 g = $$\frac{x}{120}$$  and    S.P. of 1 g =$$\frac{x}{150}$$​​

​$$\text{Loss per gram} = \frac{x}{120} - \frac{x}{150}$$$$= \frac{x}{600}.$$​​​

​$$\text{Percentage Loss} = \frac{\frac{x}{600}}{\frac{x}{120}} \times 100 = \frac{120}{600} \times 100 = 20\%.$$

Option (b) is right.

Alternate Method:

Loss percentage = $$\frac{150-120}{150} \times$$​100 = 20%

Option (b) is right.