115 should do it!
About 14 bricks should do it.
Gee, a square foot is 12x12, difficult problem.
The first step is to convert the total patio area to inches so we are working with the same units. 100sq ft = 14,400 sq inches. Now we need to calculate the number of square inches each brick takes up. Answer: 36 sq in. Now we just divide the total square inches of the patio by the square inches taken up by each brick: 14,400/36 = 400 bricks. It will take 400 bricks to make a 100 square foot patio.
The question, as stated cannot be answered. You need to know two dimensions of the bricks to find the area of each brick, convert that area into square feet (if necessary) and then divide 256 by the area of each brick. Bricks are not usually square so it would not be appropriate for me to assume that the bricks are 16" by 16".
A 12 x 12 inch brick is 1 square foot. A 20 x 20 (foot) patio is 400 square feet, so you would need 400 bricks.. this assumes you are butting the bricks fairly tight, not leaving large seperations between them, etc...
The answer will depend on the shape of the patio. If it curved then some bricks will need trimming and that will result in wastage and so a larger number of bricks will be required. Also, if the patio leaves a small fractional amount after a whole number of bricks, you will need a lot more bricks. As an extreme example, if the patio is 8 cm*625 metres then you will need 3125 bricks. However, if the shape is convenient, you will require 2500 bricks.
Each brick has an area of 1ft x 1ft ie 1 sq foot. So you would need 308 bricks.
If the bricks are in feet then 51/2 bricks would be needed.