Once I had been to the post-office to buy stamps of five rupees, two rupees and one rupee. I paid the clerk Rs $20$, and since he did not have change, he gave me three more stamps of one rupee. If the number of stamps of each type that I had ordered initially was more than one, what was the total number of stamps that I bought?
Given that the number of stamps of each type that he had ordered initially was more than one, so they're at least 2.
$\therefore$ Cost incurred = 2*5 + 2*2 + 2*1 = 16
But he had to pay a sum of 17, so the extra stamp must be of Re. 1.
Also the clerk did not have any change so instead he gave 3 more stamps of Re.1
So total stamps he bought = 6 + 1 + 3 = 10
A is the answer.