Round 189.939360828 to 4 decimal places.

Ineed i been stuck on this question since yesterday

Can someone tell me if this is perpendicular? !

Marquise has 200 meters of fencing to build a rectangular garden. the garden's area (in square meters) as a function of the garden's width w w (in meters) is modeled by: a ( w ) = − w 2 + 1 0 0 w a(w)=−w 2 +100w what side width will produce the maximum garden area? meters