First we need to find out the area of the rectangular kitchen room.
Length of room is 20 ft and width is 10 ft.
So, area of rectangle = 20 x 10 = 200 ft²
The tiles costs $2.50 per square feet. Since the total area is 200 square feet, the total cost will be:
Total cost = Cost of tile per square feet x Total area
Total cost = 2.5 x 200
Total cost = $500
Thus, it will cost John $500 to tile his kitchen