A vendor sold 5 chocolates for ₹1, thereby gaining 40%. How many chocolates did he buy for ₹1?

Correct option is D

Given:

Selling rate: 5 chocolates for ₹1 

SP per chocolate = ₹$$\frac{1}{5} = 0.20$$​ 

Profit = 40%

Formula Used:

Profit% = $$\frac{\text{SP} - \text{CP}}{\text{CP}} \times 100$$​​

Hence,$$\text{SP} = \text{CP} \times (1 + \frac{\text{Profit\%}}{100})$$​​

Solution:
​$$\text{SP} = 1.40 \times \text{CP}$$​​

​$$\text{CP} = \frac{\text{SP}}{1.40}$$​​

So, CP per chocolate $$= \frac{0.20}{1.40} = \frac{2}{14} = \frac{1}{7}$$​ rupee.
Therefore, with ₹1, number of chocolates bought =$$\frac{1}{\frac17} = 7$$​​

Alternate Method:
Profit 40%

SP : CP = 140 : 100 = 7 : 5.
If SP for 1 chocolate = ₹$$\frac{1}{5}$$​, then

CP for 1 chocolate =$$\frac{5}{7} \times \frac{1}{5} = \frac{1}{7}$$​ rupee

₹1 buys 7 chocolates.