$1\mathrm{.}8$ Answer the following :

$($a$)$ You are glven a thread and a metre scale. How will you estimate the diameter of the thread?

$($b$)$A screw gauge has a pitch of $1\mathrm{.}0$ mm and $200$ divisions on the circular scale. Do you think it is possible to increase the accuracy of the screw gauge arbitrarlly by increasing the number of divistons on the circular scate?

$($c$)$ The mean diameter of a thin brass rod is to be measured by vernter callipers. Why is a set of $100$ measurements of the diameter expeeted to yield a more reliable estimate than a set of $5$ measurements only?