F4 Maths...Long question唔識做!求solution!
2006-11-05 3:23 am
Two cars X and Y are 500 km and 300km away from city A.They start travelling to city A at the same time with constant speeds below 100 km/h.If car X reaches city A half an hour later than car Y and the speed of car Y is 15km/h less than car X,find the speeds of the two cars.(Answer is the speed of car X = 40km/h and the speed of car Y = 25km/h)
回答 (1)
2006-11-06 2:10 am
✔ 最佳答案
Let x be the speed of car Xso speed of Y is x-15
time taken for X to reach A is 500/x and time taken for Y to reach A is 300/(x-15)
500/x-300/(x-15)=0.5(half and hour=0.5 hr)
x^2-415x-15000=0
x=40 or x=375 (rejected, becauseThey start travelling to city A at the same time with constant speeds below 100 km/h, x must be less than 100)
so speed of X is 40km/h
speed of Y is 40-15=25km/h
參考: me
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