# Sara has a fire in the fireplace to warm her 20°C apartment. She realizes that she has left the iron poker in the fire. How hot is the fire if the 0.60 m poker lengthens 0.30 cm? (αiron = 12 x 10-6°C-1)

$\Delta l = {l}_{0} \alpha \Delta T$
Where ${l}_{0}$ is the initial/original length, $\alpha$ is the linear expansion coefficient and $\Delta T$ is the variation of temperature.
$0.3 = 60 \cdot 12 \times {10}^{-} 6 \cdot \left({T}_{f i r e} - 20\right)$
So: T_(fire)=437°C