How many 4.8 meter decking boards do i need to buy to cover an area 11 meters x 6 meters?

i want to put some decking in my garden , the area i want to cover is 11 meters by 6 meters, i would like to use decking boards that are 4.8 meters long , how many will i need to buy? Also how many joists will i need to buy for the frame, it will be built on top of an existing patio which is perfectly level. thanks!