If the Cost price of an article is 40% of its selling price, then what percent is the selling price of its cost price?

Correct option is A

Given:

The cost price of an article is 40% of its selling price.

We need to find what percent the selling price is of the cost price.

Solution:​

Let the selling price be SP and the cost price be CP.

​$$CP = 40\% \, \text{of} \, SP = \frac{40}{100} \times SP = 0.4 \times SP$$

we want to find

​$$\frac{SP}{CP} \times 100$$​

From the equation CP = 0.$$4 \times SP$$​, we can write:

SP =$$\frac{CP}{0.4}$$​

​$$\frac{SP}{CP} \times 100 = \frac{\frac{CP}{0.4}}{CP} \times 100 = \frac{1}{0.4} \times 100 = 2.5 \times 100 = 250\%$$​​

The selling price is 250% of the cost price.

Alternate Method:

$$CP = 40\% \, \text{of} \, SP$$

$$\frac{CP}{SP} =\frac {40}{100}= \frac {2}{5}$$

Now,

​$$\frac{SP}{CP} \times 100=$$$$\frac 52 \times 100 = 250\%$$​​​