For which material does resistivity decrease with an increase in temperature?

The temperature coefficient of resistance of a resistor wire is $0.00125\,^{\circ}C^{-1}$. At $300\,K$,its resistance is $1\,\Omega$. At what temperature in $K$ will its resistance be $2\,\Omega$?

If the length of a wire is increased by $0.1\%$,what is the percentage increase in its resistance (in $\%$)?

$A$ $1\,m$ long wire is broken into two unequal parts $X$ and $Y$. The $X$ part of the wire is stretched into another wire $W$. The length of $W$ is twice the length of $X$ and the resistance of $W$ is twice that of $Y$. Find the ratio of the length of $X$ to the length of $Y$.

By increasing the temperature,the specific resistance (resistivity) of a conductor and a semiconductor,respectively,is:

Why does the resistivity of metals increase with an increase in temperature?