1條maths
2009-06-03 1:54 am
The distance between two cities is 120km. If one drives 10km/h faster, he can travel from one city to the other ten minutes earlier. Find the percentage increase of the speed.
回答 (2)
2009-06-03 2:14 am
✔ 最佳答案
Let the original speed be x km/hthe original time required=120/x hour
the new time required=(120/x)-(1/6) hour
on the other hand , the new time required=120/(x+10)
(120/x)-(1/6)=120/(x+10)
(720-x)/6x=120/(x+10)
(720-x)(x+10)=120(6x)
720x-x^2+7200-10x=720x
x^2+10x-7200=0
x=80 or x=-90 (rejected)
The percentage increase of the speed
=(10)/(80) *100%
=12.5%
2009-06-09 1:47 am
bad
2009-06-23 16:41:35 補充：
It is so bad
2009-06-23 16:41:35 補充：
It is so bad
收錄日期: 2021-04-22 00:39:14
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20090602000051KK01061