Characteristic strength of M20 concrete is 20 MPa. What is the number of cubes having 28 days compressive strength greater than 20 MPa out of 100 cubes made with this?

Correct option is B

The characteristic strength of concrete, as defined by IS 456:2000, is the strength below which not more than 5% of the test results are expected to fall.
For M20 concrete, the characteristic compressive strength at 28 days is 20 MPa.
Out of 100 cubes, it is expected that 95 cubes will have compressive strength greater than 20 MPa, while 5 cubes may have strength less than or equal to 20 MPa due to natural variability in concrete properties.