Answer:
[tex]39.29\ \text{km/h}[/tex]
Step-by-step explanation:
s = Speed of the train
m = Money spent on maintanence
[tex]s\propto m^{\dfrac{1}{3}}[/tex]
Let k be the constant of proportionality so
[tex]s=k (m)^{\dfrac{1}{3}}[/tex]
Now a case is given where 25 km/hr is possible on a stretch for which 450,000 is spent so
s = 25
m = 450000
[tex]s=k (m)^{\dfrac{1}{3}}\\\Rightarrow k=\dfrac{s}{m^{\dfrac{1}{3}}}\\\Rightarrow k=\dfrac{25}{450000^{\dfrac{1}{3}}}\\\Rightarrow k=0.326[/tex]
Now when m = 1750000
[tex]s=k (m)^{\dfrac{1}{3}}\\\Rightarrow s=0.326\times 1750000^{\dfrac{1}{3}}\\\Rightarrow s=39.29\ \text{km/h}[/tex]
The maximum speed of the train would be [tex]39.29\ \text{km/h}[/tex].