想問下呢題點計：
David drove his car at a uniform speed of 30km/h for a certain journey. If the journey is increased by 20% in distance and he wanted to reduce the total time taken for the journey by 10%, at what speed should he drive his car?
中3數學percentages
2011-06-11 11:11 pm
回答 (1)
2011-06-12 1:06 am
✔ 最佳答案
Let original speed v = 30, distance = s and time = ts = 30t
Now, s' = 1.2s and t = 0.9t, want v'
As v' = s'/t' = 1.2s/0.9t = (4/3)(30) = 40 km/h
So, he should drive his car with speed 40 km/h
2011-06-11 17:06:21 補充：
t' = 0.9t
收錄日期: 2021-04-26 14:55:06
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20110611000051KK00556