The mean diameter of a thin brass rod is to be measured by vernier callipers. Why is a set of 100 measurements of the diameter expected to yield a more reliable estimate than a set of 5 measurements only?

A spherical glass vessel has a cylindrical neck 8 cm long,2 cm in diameter,the diameter of the spherical part is 8.5cm.By measuring the amount of water it holds,a child finds its volume to be 345cm^3 .Check whether she is correct,taking the above as the inside measurements,and pi=3.14 .

A student measures the thickness of a human hair by looking at it through a microscope of magnification 100. He makes 20 observations and finds that the average width of the hair in the field of view of the microscope is 3.5 mm. What is the estimate on the thickness of hair?

A zinc rod is measured by means of a brass scale (Which is correct at 0°C ) and is found to be 1.0001 metre long at 10°C .What is actual length of the rod at 0°C ?( alpha forZn= 29*10^-6/°C , alpha for brass= 19*10^-6/°C ).