Question

A wire of 100 ohm resistance is cut into how many equal pieces so that when they are connected in parallel resultant r is 1 ohm

Answer 1

when wire is cut in n parts each part will be having 100/n resistance.
parallel combination of n 100/n resistors =100/n^2

ATQ,
$\frac{100}{ {n}^{2} } = 1 \\ 100 = {n }^{2} \\ n = 10$