Usual speed is given by :
[tex]s = \dfrac{45\times 60}{35} \ mph\\\\s=77.14 \ mph[/tex]
Now, we want to reach job exactly at 10 : 00 .
So, time taken is , t = 10:00 - 09:30
t = 30 minutes = 0.5 hours .
New speed is :
[tex]s'= \dfrac{45}{0.5} = 90 \ mph[/tex]
Therefore, increase in speed is ( 90 - 77.14 ) = 12.86 mph.
Hence, this is the required solution.
