1 |
20 |
1 |
28 |
平时水速是:(
1 |
20 |
1 |
28 |
1 |
140 |
现在是水速是:
1 |
140 |
1 |
70 |
现在顺水速度是:
1 |
20 |
1 |
140 |
1 |
70 |
2 |
35 |
1 |
28 |
1 |
140 |
1 |
70 |
1 |
35 |
顺水时间是:1÷
2 |
35 |
逆水时间是:1÷
1 |
35 |
从A到B再回A共需:17.5+35=52.5(小时).
答:从A到B再回到A共需52.5小时.
故答案为:52.5.
1 |
20 |
1 |
28 |
1 |
20 |
1 |
28 |
1 |
140 |
1 |
140 |
1 |
70 |
1 |
20 |
1 |
140 |
1 |
70 |
2 |
35 |
1 |
28 |
1 |
140 |
1 |
70 |
1 |
35 |
2 |
35 |
1 |
35 |