Maths --- percentage
2007-11-22 4:41 am
On travelling over the same distance, if the speed is increased by 25%, what is the percentage change in the time taken?
回答 (2)
2007-11-22 4:47 am
✔ 最佳答案
Let x be the total distance and v be the original speed.Original time taken = x/v
If speed is increased by 25%, new speed = v(1+25%) = 1.25v
Time taken for the new speed = x/1.25v = 0.8x/v
Percentage change = (0.8x/v - x/v) / (x/v) * 100%= -0.2*100% = -20%
It saves 20% of time taken
2007-11-22 5:00 am
Let v, s, t, t1 be the speed, distance, initial time taken, final time taken respectively
v = s / t
When speed is increased by 25%,
(1 + 25%)v = s / t1
125%(s / t) = s / t1
t1 = t / 1.25
t1 = (4 / 5)t = 80%t
Thus when speed is increased by 25%,
time taken is decreased by 20%.
v = s / t
When speed is increased by 25%,
(1 + 25%)v = s / t1
125%(s / t) = s / t1
t1 = t / 1.25
t1 = (4 / 5)t = 80%t
Thus when speed is increased by 25%,
time taken is decreased by 20%.
收錄日期: 2021-04-13 18:12:08
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20071121000051KK03567