Why does it take 10 copies of 1 sixth to make the same amount as 5 copies of 1 third?

This is because (1/3) = (2/6). 10 copies of (1/6) = (10/6) and 5 copies of (2/6) = (10/6) too. (1/3) is just the most simplified form for (2/6)

Yes i also think it is b