Maths-
General
Easy

Question

# George took a nonstop flight from Dallas to Los Angeles, a total flight distance of 1,233 miles. The plane flew at a speed of 460 miles per hour for the first 75 minutes of the flight and at a speed of 439 miles per hour for the remainder of the flight. To the nearest minute, for how many minutes did the plane fly at a speed of 439 miles per hour?

Hint:

## The correct answer is: 90

### The total distance between Los Angeles and Dallas is 1233 miles.So, total distance covered = 1233 miles.Initially,Speed of the plane = 460 miles per hourTime taken = 75 minutesWe convert the time in hours as the speed is given in miles per hour.As, 60 minutes = 1 hourSo, we get, 75 minutes =   =   = 1.25 hoursThus, time taken = 1.5 hoursWe know,Rewriting the equation , we haveThus, the distance travelled initially is given byThus, the distance covered by the flight in the first 75 minutes while  the speed was 460 miles per hour = 575 milesNext,Remaining distance to travel = 1233 – 575 = 658 milesFor the second part of the journey,Speed of the plane = 439 miles per hourDistance travelled = 658 milesRewriting the above formula, we getUsing the above quantities, we getConverting the time into minutes, we have,Thus, the number of minutes for which the plane flies at speed 439 miles per hour = 90 minutes.

Note:
The relation between speed, distance and time given by the relation above is very important. There could be many such questions formed which ask us to calculate any of the three quantities with certain conditions involved.