Chapter 2, Problem 13P

Solution

Total time for the trip and average speed of the plane for the trip.

6.75 hours and 874.07 km/h

Given:

An airplane travels 3100 km at a speed of 790 km/h. For the next 2800 km its speed is 990km/h Formula used:

  $v=\frac{d}{t}$ Here v is speed, d is distance and t is time.

Calculation:

Let time taken to complete 3100km at a speed of 790 km/h is t₁

So,

  $t_1=\frac{3100}{790}$ =3.92 hours

For the next 2800 km its speed is 990km/h. Let the time taken to complete 2800km is t₂ So $t_2=\frac{2800}{990}$

  $t_2=2.83$ hours

Total time for the trip= $t_1+t_2$

Total time= 3.92+2.83= 6.75hours

Total distance $d=3100+2800$

  $d=5900$ km

Total time $t=6.75$ hours

So average speed is

  $v=\frac{5900}{6.75}=874.07\text{km}/\text{h}$

Conclusion:

Therefore, time taken is 6.75 hours and average speed is 874.07 km/h.