更新1:
答案有少少出入，係6.5hr
inequalities(4)
2011-11-30 6:15 am
Mr. Lee drove from town A to town B at 65km/h. Half an hour later. Mr. Ho drove along the same route from town A to town B at 80km/h. At least how long would it take for Mr. Ho to be not less than 65 km ahead of Mr. Lee?
回答 (2)
2011-11-30 4:49 pm
✔ 最佳答案
Suppose at this moment, Mr. Lee has driven for x hours, then Mr. Ho has driven for (x - 0.5) hours.We have:
80(x - 0.5) >= 65x + 65
80x - 40 >= 65x + 65
15x >= 105
x >= 7
So it takes 7 hours.
參考: 原創答案
2011-12-01 8:17 pm
Let x hr be the time taken that Mr. Ho is not less not 65km ahead of Mr. Lee
Mr. Lee drove 0.5 hr before Mr. Ho, the distance drove is 65km/h * 0.5=32.5km
80km/h * x -65km/h *x >32.5km + 65km
15x >97.5
x>6.5
2011-12-01 12:20:37 補充：
sorry, 所有符號應該是 " >="
80*x-65*x >=32.5+65
15x>=97.5
x>=6.5
so, Mr. Ho would take 6.5 hrs
Mr. Lee drove 0.5 hr before Mr. Ho, the distance drove is 65km/h * 0.5=32.5km
80km/h * x -65km/h *x >32.5km + 65km
15x >97.5
x>6.5
2011-12-01 12:20:37 補充：
sorry, 所有符號應該是 " >="
80*x-65*x >=32.5+65
15x>=97.5
x>=6.5
so, Mr. Ho would take 6.5 hrs
收錄日期: 2021-04-20 11:55:07
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20111129000051KK00914