there are approximately

20 wheelbarrows in 1m3 of concrete
10 wheelbarrows in 0.5m3 of concrete
5 wheelbarrows in 0.25m3 of concrete

mix your own concrete

Use: Small Volume: Volume to make 1m3 of concrete:
General purpose Footpaths and Mowing strips 1 Part Cement
7 Parts Builders Mix
6 Bags Cement
1.25m3 Builders Mix
Paving, Concrete Driveways (use of Ready Mix preferred) 1 Part Cement
5.5 Parts Builders Mix
7.5 Bags of Cement
1.20m3 Builders Mix
Bedding Concrete Fence posts Clothes lines 1 Part Cement
8.5 Parts Builders Mix
5 Bags of Cement
1.25m3 Builders Mix

calculations

To calculate the volume of concrete needed in a rectangle or square the formula is:
Length times Width times Depth
10m long times 5m wide times 100mm deep = 10*5*0.1= 5.0m3
To calculate the volume of concrete needed in a triangle the formula is:
½ Base  times  Height  times  Depth