Problem:
The rock group Loco Moco was scheduled for a concert at the Blaisdell Concert Hall. Because it was the concert highlight of the year, there was excitement in the air and people were eager to get tickets, which could only be purchased in person. Hours before tickets were to go on sale, people were lined up to buy tickets. In fact, the first person came 12 hours before the ticket booth was open. A new group of ticket buyers joined the line every 30 minutes.
Mission:
If each new group has four persons more than the previous group, how many people were in line after the 20th group joined, assuming the first person is the first group?
If each new group had two persons more, how do you think the number in line after the 20th group joined compares to the number of people line when four people joined as described in problem 1?
I need a pattern