SOLUTION: Solve an Equation: I am having alot of trouble setting up this equation to solve. The owners of a theater plan to reconfigure the seating. Adding 4 rows, they can reduce the numb

Algebra ->  Customizable Word Problem Solvers  -> Misc -> SOLUTION: Solve an Equation: I am having alot of trouble setting up this equation to solve. The owners of a theater plan to reconfigure the seating. Adding 4 rows, they can reduce the numb      Log On

Ad: Over 600 Algebra Word Problems at edhelper.com


   



Question 434075: Solve an Equation: I am having alot of trouble setting up this equation to solve.
The owners of a theater plan to reconfigure the seating. Adding 4 rows, they can reduce the number of seats per row by 2 without changing capacity. If, instead, they add 5 seats per row, they can reduce the number of rows by 7, thus decreasing capacity by 1 seat. What is the theater's current capacity? (Assume that each row has the same number of seats.

Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
The seating capacity can be expressed as
(number of rows)*(seats/row)
Let r = number of rows
Let s = number of seats per row
given:
(1) +%28+r+%2B+4+%29%2A%28+s+-+2%29+=+r%2As+
(2) +%28+r+-+7%29%2A%28+s+%2B+5+%29+=+r%2As+-+1+
--------------------------
(1) +r%2As+%2B+4s+-+2r+-+8+=+r%2As+
(1) +4s+-+2r+=+8+
and
(2) +r%2As+-+7s+%2B+5r+-+35+=+r%2As+-+1+
(2) +-7s+%2B+5r+=+34+
------------------
Multiply both sides of (1) by 5 and
multiply both sides of (2) by 2
Then add the equations
(1) +20s+-+10r+=+40+
(2) +-14s+%2B+10r+=+68+
+6s+=+108+
+s+=+18+
and, since
(1) +4s+-+2r+=+8+
(1) +4%2A18+-+2r+=+8+
+72+-+2r+=+8+
+2r+=+72+-+8+
+2r+=+64+
+r+=+32+
Current capacity = +18%2A32+=+576+
check:
(2) +%28+r+-+7%29%2A%28+s+%2B+5+%29+=+r%2As+-+1+
(2) +%28+32+-+7%29%2A%28+18+%2B+5+%29+=+576+-+1+
+25%2A23+=+575+
+575+=+575+
OK