A 20-row theater has three sections of seating. In each section, the number of seats in a row increases by one with each successive row. The first row of the middle section has 10 seats. The first row of each of the two side sections has 4 seats.
a. Find the total number of chairs in each section. Then find the total seating capacity of the theater.
b. Write an arithmetic series to represent each section.
*I am a little confused on what the upper limit would be for a summation notation. I will write a formula of what I mean.

Question

A 20-row theater has three sections of seating. In each section, the number of seats in a row increases by one with each successive row. The first row of the middle section has 10 seats. The first row of each of the two side sections has 4 seats. 
a. Find the total number of chairs in each section. Then find the total seating capacity of the theater.
b. Write an arithmetic series to represent each section.
*I am a little confused on what the upper limit would be for a summation notation. I will write a formula of what I mean.

anonymous · Answer

I don't know the upper limit (?) and this would be the formula for the side sections: $$\sum_{n=4}^{?}n$$ 

I don't know the upper limit (?) and this would be the formula for the middle section: $$\sum_{n=10}^{?}n$$

anonymous · Answer

Lol nvm, I get it now.