Math question 2
2006-10-28 2:29 pm
A man cycled 15 km from A to B at a uniform speed. If he had increased his speed by 4 km/h, he would have arrived at B one hour earlier. Find his original speed.
回答 (2)
2006-10-28 2:35 pm
✔ 最佳答案
let his original speed is x, using t hoursthen his new speed is x+4, using t-1 hours
According the question
xt=15...(1)
(x+4)(t-1)=15...(2)
from the (2)
xt-x+4t-4=15
x=4-4t
sub into (1)
4t(t-1)=15
4t^2-4t-15=0
(t-2.5)(t+1.5)=0
t=2.5 or -1.5 (rejected)
x=15/t=15/2.5=6
his original speed is 6km/hr
2006-10-28 8:39 pm
let his original speed is x, using t hours
then his new speed is x+4, using t-1 hours
According the question
xt=15...(1)
(x+4)(t-1)=15...(2)
from the (2)
xt-x+4t-4=15
x=4-4t
sub into (1)
4t(t-1)=15
4t^2-4t-15=0
(t-2.5)(t+1.5)=0
t=2.5 or -1.5 (rejected)
x=15/t=15/2.5=6
his original speed is 6km/hr
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then his new speed is x+4, using t-1 hours
According the question
xt=15...(1)
(x+4)(t-1)=15...(2)
from the (2)
xt-x+4t-4=15
x=4-4t
sub into (1)
4t(t-1)=15
4t^2-4t-15=0
(t-2.5)(t+1.5)=0
t=2.5 or -1.5 (rejected)
x=15/t=15/2.5=6
his original speed is 6km/hr
希望幫到你 求你選我最佳答案
求下你
唔該!!!!!!
唔該!!!!!!
參考: me
收錄日期: 2021-04-25 16:49:07
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