Answer
See answers.
Work Step by Step
a. Convert $4000^{\circ}C$ to kelvin.
$$4000+273.15 \approx 4300\;K$$
Convert $15\times {10^{6}}^{\circ} C$ to kelvin.
$$15\times10^6+273.15 \approx 15\times10^6\;K$$
b. Find the percentage error in each case.
$$\%\;error=100\frac{\Delta T}{T_K}=100\frac{273.15}{T_K}$$
First for $4000^{\circ}C$.
$$100\frac{273.15}{4273.15}\approx 6.4\%$$
Next for $15\times{10^6}^{\circ}C$.
$$100\frac{273.15}{15\times10^6}\approx 1.8\times10^{-3}\%$$
