8. Every day, Xiaoming has to pass through a flat section $A B$, an uphill section $B C$, and a downhill section $C D$ on his way to school (as shown in the right figure). It is known that $A B: B C: C D=1: 2: 1$, and the speed ratio of Xiaoming on the flat section, uphill section, and downhill section is $3: 2: 4$. What is the ratio of the time Xiaoming spends going to school and coming back home? $\qquad$
Analysis: A journey problem related to the ratio of fractions.
Let the entire journey be "1", then the distances of the flat road, uphill road, and downhill road on the way to school are $\frac{1}{4}, \frac{1}{2}, \frac{1}{4}$, respectively. On the way back home, the distances of the flat road, uphill road, and downhill road are $\frac{1}{4}, \frac{1}{4}, \frac{1}{2}$, respectively. The ratio of the time Xiao Ming spends going to school to the time he spends coming back home is:
$$
\left(\frac{1}{4} \div 3+\frac{1}{2} \div 2+\frac{1}{4} \div 4\right):\left(\frac{1}{4} \div 3+\frac{1}{2} \div 4+\frac{1}{4} \div 2\right)=19: 16
$$