Question 35039

# of people = -100x^2 + 1200x

for 2000 people to be there,

2000 = 100x^2 + 1200x

re-arranging,

-100x^2 + 1200x = 2000

i.e. -x^2 + 12x = 20

-x^2 +12x -20 = 0
-x^2 + 10x + 2x - 20 = 0

solve, you get x = 2hrs