The Pen percentage problem is as follows :

Suppose I go to a bookstall and purchase 11 pens for 10 Rs. But then I go ahead and sell all those pens at the rate of : 10 pens for 11 Rs. What is my profit percentage ?

a). 80 %

b). 21 %

c). 12 %

d). 10 %

The solution is given as follows :

**EXPLANATION :**

Consider how much I spent Initially : 10 rs for 11 pens.

Now I sold all those pens at a new price. So the first 10 pens sold for 11 Rs. and the remaining one pen sold for 1.1 Rs (Since 10 sold for 11 Rs)

Hence I now have 11 + 1.1 = 12.1 Rs.

Since I initially spent 10 Rs and I now have 12.1 Rs, my profit percentage will be **(**(12.1 – 10)/10**)** * 100% = 21%

Hence the answer is **(b) 21 %**

If you have any doubts, leave me a comment below! ðŸ˜‰