A和B二人比賽賽跑,如果二人一起向同一方向跑(一圈400米),由於B的爆發力比A強,一開始比A快,但B在一鐘三十秒後追上B.如果二人反方向跑,他們30秒後就遇上(一圈400米).問A和B的時速?
設X是A的時速
設Y是B的時速
請詳解和計算答案
中二數學的問題
2008-12-05 5:18 am
回答 (1)
2008-12-05 5:44 am
✔ 最佳答案
Distance travelled by A in 90 second = 90X.Distance travelled by B in 90 second = 90Y = 400 + 90X
therefore, 9Y - 9X = 40.............(1)
When running in opposite direction,
distance travelled by A = 30X.
distance travelled by B = 30Y
so 30Y + 30X = 400
3Y + 3X = 40.....................(2)
(2) x 3 + (1) we get
18Y = 160
Y = 80/9 m/s.
X = (40 - 240/9)/3 = 40/9 m/s.
收錄日期: 2021-04-25 22:35:45
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20081204000051KK01668