the picture in the attached figure
we know that
To know the amount of cubic feet needed, calculate the volume of the stair
we can divide the stair into three rectangular prisms
Volume rectangular prism N 1=6*9*1.5----> 81 ft³
Volume rectangular prism N 2=6*6*1.5----> 54 ft³
Volume rectangular prism N 3=6*3*1.5----> 27 ft³
total volume=81+54+27-----> 162 ft³
the answer is
162 ft³ of concrete are needed
