Question

A plane left 30 min. late than it's schedule time and in order to reach it's destination 1500km away in time, it has to increase it's usual speed. Determine it's usual speed

Answer 1

Answer:

500 km / hr

given:

Late = 30 min

Distance = 1500 km

Speed increase = 100 km / hr

Step-by-step explanation:

By formula,

Speed = Distance / Time

Since the time is unknown,

Consider x for time,

Speed original = 1500 / x  

Time taken = ( x - 1 / 2 )

Therefore,

Substituting the value of x,

Speed new = 1500 / (x - 1/2)

Speed  New - Speed original = 100

( 1500 / ( x - 1 / 2 ) ) - ( 1500 / x ) = 100

 150 ( ( 10 / x - 1 / 2 ) - 10 / x = 100 

30 x -30 x +15 = 2x^2 - x

15 = 2x^2 - x

2x^2 - x -15 = 0

Solving,

x = -5/2

x = 3

As time cannot be negative,

The usual time taken by the plane is 3 hr

Speed original = ( 1500 / 3 ) = 500 km / hr

Hence, the usual speed of the plane is 500 km / hr

(answer)

Answer 2

let be the time =60×60=3600

then x-30= 3600-30=3570

distance =1500km

then speed of plane = distance ÷time

=1500÷3570

=42/10

hope its help