# Increasing Row Size

1. Nov 17, 2007

### Blueshy

Increasing Row Size....

1. The problem statement, all variables and given/known data
There are 150 rows at a concert hall. Each row you move back there is an increase of 10% in the number of seats. The first row has 100 seats. How many seats are there in the concert hall?

2. Relevant equations
I don't know the equation to represent this change.

3. The attempt at a solution
Obviously I could go through and do each rows amount of seats, but I'd like to know the equation that will solve this. Is it n(n+1)/2?

2. Nov 17, 2007

### Dick

It's called a geometric series. The number of seats in the nth row is 100*(1.1)^n (where n=0 is the first row). Now find a reference and look for 'geometric series'.

3. Nov 17, 2007

### dynamicsolo

Notice that the number of seats in each successive row increases by a constant proportion, that is, each row has 1.10 times as many seats as the preceding row. What kind of a sequence is this?

If you have to add a finite number of terms of a sequence of this type, what formula do you use?

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