Question: A massive number of placards are placed in a huge basket at the entrance of a stadium. Every person entering the stadium collects placards one for each hand. People started entering the stadium at 3 pm. After few minutes, people complained that the basket is empty and there is no more placard. If the basket can hold 6450 placards and it was full in the beginning, how many people have entered the stadium till that time?
Answer: 3225