[填空题]
A hot apple pie was t f-2l98ycmzifakef (;f;kmk l7 ghdgm:3uhln9n* n out of the oven and left cooling on the bench. The temperatureteuhf : dk3km79gh(*nl;ng; lmfmperature of the kitchen is $19^{\circ}C$ This situation can be modelled by the exponential function T=a+b($k^{−t}$), where T is the temperature of the appleapple pie, in$^{\circ}C$, and t is the number of minutes for which the apple pie has been on the bench in the kitchen. A sketch of the situation is given below.
1.Explain why a=19.
Initially, at t=0, the temperature of the apple pie is $180^{\circ}C$.
2.Find the value of b.
After being left cooling on the bench for one minute, the temperature of the apple pie is $159^{\circ}C$. b =
3.Show that k=1.15.
4.Find the temperature of the apple pie five minutes after it has been left cooling on the bench. T ≈ $^{\circ}C$
5.Find the total time needed for the apple pie to reach a temperature of $30^{\circ}C$. Give your answer in minutes and seconds, correct to the nearest second. t ≈ min
