You are laying a concrete border around a circular pond. the pond is 7 metres in diameter and is surrounded by a path 2 metres wide. the concrete needs to be 50 millimetres deep. you are using premixed bagged concrete. 1 cubic metre (m³) requires 106 x 20 kg bags. how many 20 kg bags of premixed concrete do you need? round your answer to the nearest whole number.

We find the volume of the path in cubic meters and multiply by 106 bags per cubic meter.

The path is an annulus with inner radius r=7 m and outer radius s=7+2=9 m and depth in meters d=50/1000 = 0.05 m.

The volume is the area of the path times its depth; the area is the difference of the area of the outer and inner circles of the annulus.

We need

533

do you have a picture of the table