So you need to know the area of patio in cm, so you need to caculate area and than convert.
4 x 5 = 20 m
20 m = 200000 cm
once you know area, you need to know the area of bricks.
9.5 x 20 = 190
Than divide patio area by brick area
200000 divide 190 = 1052 .63
since there cant be 1052.63 bricks, just round up to 1053.
so 1053 bricks are required for this patio.
Hope this helped!