How much does a 45% solution of de-icing fluid lower freezing point of water?

It lowers the freezing point by 30 °C

Explanation:

In the picture attached, the curve freezing point vs de-icing fluid concentration is shown. We can see that a 45% solution of de-icing fluid makes the freezing point of water -30 °C, that is, 30 °C below the pure water freezing point.

answer: semi-infinite solid initially at a uniform temperature of 400 ◦c is cooled at its surface by convection. the cooling fluid at a constant temperature of 200 ◦c has a convective coefficient (ha) of 250 w/m2.k. the physical properties of the solid: k = 20 w/m.k and α = 4 * 10-5  m2/s. using δx = 0.04 m and δt = 10 s. write the finite difference equations describing the transient heat transfer of the first five δx and the temperature profile after 30 s.