Answer
The average temperature is approximately $21.21^{\circ}$ Celsius.
Work Step by Step
Simpson's Rule states that
$T_{n}=\dfrac{1}{3}[y_0+4y_1+2y_2+..+4y_{N-3}+2y_{N-2}+4y_{N-1}+y_N]\Delta x$
Since, $\Delta t=15 \ min=\dfrac{1}{4} \ hour $
Thus, using Simpson's Rule, we have:
$S_{12}= \dfrac{1}{3}[v_0+4v_1+2v_2+..+4v_{9}+2v_{10}+4v_{11}+v_{12}]\Delta t$
Now,
$T_{avg}=\dfrac{1}{3} S_{12}=(\dfrac{1}{3}) (\dfrac{1}{3})(\dfrac{1}{4} )[21+4(21.3)+2(21.5)+4(21.8)+2(21.6)+4(21.2)+2(20.8)+4(20.6)+2(20.9) +4(21.2)+2(21.1)+4(21.3)+21.2] \approx 21.21$
Hence, the average temperature is approximately $21.21^{\circ}$ Celsius.
