I'm stumped on this problem...it should be easy...
Suppose that 50 steel wires of diameter 0.5 mm can just support a particular weight without breaking. What would the diameter of a single steel wire have to be in order to just support the same weight without breaking? Explain how you found your answer.
If the thin wires and the single fat wire have the same tensile strength, then the proportion is by cross-sectional areas only.
50[pi* (0.5/2)^2] = 1[pi *(d/2)^2]
where d is the diameter of the fat wire in cm.
If the thin wires have X tensile strength and the fat wire has Y tensile strength, then,
50[pi* (0.5/2)^2](X) = 1[pi *(d/2)^2](Y).
However, my understanding of the question is that all wires being made from the same material is implied (otherwise there's clearly not enough information to answer it). Perhaps you should ask whoever set the question for clarification ....