Tuesday

October 21, 2014

October 21, 2014

Posted by **Riana** on Sunday, January 27, 2013 at 1:42am.

- math help! -
**Stephen**, Sunday, January 27, 2013 at 7:37amSolve using aritmetic progression and quadratic equation, how?

Sum of AP = n/2(2a+(n-1)d)

Where n is the number of terms, ie in your case the number of rows of seats, 'a' is the number in the first row (a=262) and 'd' is the difference in the next row (d=18). Sum of AP is the number of seats in the arena (Sum=15690). Put this together and you get:

15690=n/2[2*262+(n-1)18]

18n^2+506n-31380=0

equation to: ax^2+bx+c,; a=18, b=506, c=-31380

Now comes the quadratic, solution to a quadratic =

[-b(+/-)Sqrt(b^2-4ac)]/2a

substitute the values of a,b anc from above into the quadratic and solve.

n=30.

Please always check your answer, in this case use sum of AP.

**Answer this Question**

**Related Questions**

math - Determine the seating capacity of an auditorium with 10 rows of seats if ...

Math - an auditorium has 50 rows of seats. THe first row has 20 seats, the row ...

math (plz help) - In a movie theater, theater A has 30 seats in the first row. ...

math - In a movie theater, Theater A has 30 seats in the first row. Each next ...

arithmetic - PLEASE I REALLY NEED HELP WITH THIS The seats at a local baseball ...

Discrete Mathematics - Mathematical sequences can be used to model real life ...

Math - An auditorium has 50 rows of seats. The first row has 20 seats, the ...

math - In a movie theater, theater A has 30 seats in the first row. Each next ...

Algebra 2 - The first row of a concert hall has 20 seats, and each row after the...

math (plz help) - Ms. Sue has not answered this question where all work must be ...