Solution:
Original speed =180/4 = 45 km/h.
Actual speed = 45+5 = 50km/h.
Actual time = 180/50=3.6 hours.
4-3.6= 0.4 hours in advance
19, A and B start from AB at the same time. When they met, the distance they walked was 4: 3. After meeting, B is faster than A by 12km per hour, and A still keeps the original speed. As a result, the two cars arrived at the destination at the same time. It is known that B traveled 12 hours.
Solution: Let the speeds of Party A and Party B be 4a km/h and 3a km/h respectively.
therefore
4a× 12×(3/7)/(3a)+4a× 12×(4/7)/(4a+ 12)= 12
4/7+ 16a/7(4a+ 12)= 1
16a+48+ 16a=28a+84
4a=36
a=9
A =4×9=36 km/h speed.
AB distance = 36× 12 = 432km.
Arithmetic method:
Time after meeting = 12×3/7=36/7 hours.
Speed 12km, linear speed per second 12x36/7 = 432/7km.
When we met, A was more than B. 1/7.
Then the whole journey = (432/7)/( 1/7) = 432km.
20. Two cars, A and B, drive in opposite directions from two places 325 kilometers apart at the same time. The speed of A car is 52 kilometers per hour, and the speed of B car is 65438+0.5 times that of A car. When will the cars meet?
Solution: velocity b = 52×1.5 = 78 km/h.
325/(52+78)=325/ 130=2.5.
2 1, two cars, Party A and Party B, start from A and B at the same time and drive in opposite directions. A travels 80 kilometers per hour, and B travels 10% of the whole journey per hour. When B travels to 5/8 of the whole journey, Party A can reach B through 65438+ 0/6 of the whole journey. How many kilometers is it between A and B?
Solution: 5/8 of the whole journey of Bank B = (5/8)/(110) = 25/4 hours.
AB distance = (80× 25/4)/(1-kloc-0//6) = 500× 6/5 = 600 km.
for reference only