If the selling price of 100 pens is equal to the cost price of 140 pens, find the profit percentage.

Correct option is C

Given:
100 pens selling price = 140 pens cost price
Formula Used:
Profit = SP – CP
Profit percentage =$$\frac{Profit}{CP}\times100$$​​
Solution:
As per the question;
100 SP = 140CP
​$$\frac{CP}{SP}=\frac{100}{140}\\\ \\\frac{CP}{SP}=\frac{5}{7}$$​​
Now,
Let CP = 5x and SP = 7x
Profit = 7x – 5x = 2x
Profit percentage = $$\frac{2x}{5x}\times100 = 40\%$$​​

Alternate Method:
​$$100 SP = 140 CP\\\ \\\frac{CP}{SP}=\frac{100}{140}\\\ \\\frac{CP}{SP}=\frac{5}{7}\\\ \\Profit \% = \frac{7\ -5}{5}\times100=\frac{2}{5}\times100=40\%\\\ \\$$​​