The time taken for a journey on a motorway varies inversely as
the average speed for the journey. The journey takes 1.5 h
when the average speed is 54 miles per hour. Identify the time
taken in hours for this journey when the average speed is 45
miles per hour.

Time that will be taken at speed of 45 miles/hr is 1.8 hrs

Step-by-step explanation:

Distance = Speed × Time

               = 54 × 1.5 = 81 miles

TIme = Distance/Speed

        = 81/45 = 1.8 hrs

solution:

the given function is ,

      =

the three roots of this quadratic function is , 0 ,8 and 10.all the roots are real and rational.

if a quadratic equation is of the form ,

sum of the roots = a + b +c= 0+8+10=18=  

product of roots taken two at a time = a b + b c+ c a = 0+80+0=80 =  

product of roots = a b c = 0=  

there are 11 doors in a hall starting from 0 to 11.the entry in the hall is permitted through gate number 0 and exit is allowed through only gate number 8 and 10.so, three roots(0,8,10) of quadratic function is given by entry and exit route of this hall.