Algebratown is 90km away from Numberville.
Doris drives from
Algebratown to Numberville
at 60 km/h, and then drives
back at 30km/h.
(a) Find the total time taken.
(b) Find her average speed.

The area of a rectangle is 10 cm^2. one side of the rectangle is x cm. express the perimeter of the rectangle in terms of x and show that this rectangle cannot have a perimeter of 12 cm. the perimeter of the rectangle in terms of x is __ cm