在一次徒步活动中，来自 A 组和 B 组的每位参与者都完成了 2 公里路线、5 公里路线或 10 公里路线中的一条。饼图显示了这两组中完成每条路线的人数。A 组的参与者人数是 B 组的两倍。

1. Find the total number of participants in Group B

Group A has twice as many participants as Group B. Total participants = 3 units.
$3 \text{ units} = 150$
$1 \text{ unit} = 150 \div 3 = 50$
Number of participants in Group B = $50$

2. Find the percentage of participants in Group B who completed the 2-km route

Percentage for 2-km route = $100\% - 48\% - 20\% = 32\%$

3. Calculate the number of participants for each route in Group B

2-km route: $32\% \times 50 = 16$ participants
5-km route: $48\% \times 50 = 24$ participants
10-km route: $20\% \times 50 = 10$ participants

4. Calculate the total distance walked by Group B

Total distance = $(16 \times 2) + (24 \times 5) + (10 \times 10)$
$= 32 + 120 + 100$
$= 252$ km