6. (7 points) To dig through a 300-meter-long tunnel, two construction teams, Team A and Team B, start digging from opposite ends of the tunnel simultaneously. On the first day, both Team A and Team B each dug 10 meters. Starting from the second day, Team A's work efficiency doubles every day, and Team B's work efficiency increases by 1.5 times every day. How many days will it take to dig through this tunnel? $\qquad$ days.
【Solution】Solution: Team A: 10 meters, $10 \times 2=20$ (meters), $20 \times 2=40$ (meters), $40 \times 2=80$ (meters), $80 \times 2$ $=160$ (meters)

Team B: 10 meters, $10 \times 1.5=15$ (meters), $15 \times 1.5=22.5$ (meters), $22.5 \times 1.5=33.75$ (meters), $33.75 \times$ $1.5=50.625$ (meters)

It should have taken more than 4 days. In 4 days, they completed $(10+20+40+80)+(10+15+22.5+33.75)=231.25$ (meters)
There are still $300-231.25=68.75$ (meters) left
The time needed is $68.75 \div(160+50.625)=\frac{110}{337}$ (days) or $\approx 0.326$ (days)
$$
4+\frac{110}{337}=4 \frac{110}{337} \text { (days) or } \approx 4.326 \text { (days) }
$$

Answer: The two teams need $4 \frac{110}{337}$ days to dig through the tunnel.