a student obtains resistance 3,4,12and16 ohms using only two metallic resistance wires either separately or joined .What is the value of each of these wires?

The metallic wires have resistances 12 and 4 ohm.

Therefore, when they are connected in series, total resistance = 12 + 4 = 16 ohm.

When they are connected in parallel, total resistance = [(1/12) + (1/4)]^1/2 = 3 ohm

And separately they can be used as wires of 4 and 12 ohm.