Question

mary jogs 9km at a speed of 6kmph .at what speed would she need to jog during the next 1.5 hours to have an average of9kmph for the entire jogging session

Answer 1

I hope you understand very well dear

Answer 2

Answer:

12 km/hr

Step-by-step explanation:

Mary jogs 9 km at a speed of 6 kmph

Distance  = 9 km

Speed = 6 kmph

Time = $\frac{Distance}{Speed}=\frac{9}{6}=1.5 hr$

Let x be the distance she need to jog during the next 1.5 hours

Now we are given that the average spped = 9 km/hr

Formula : $\text{Average speed} =\frac{\text{Total distance}}{\text{Total Time}}$

$9 =\frac{9+x}{1.5+1.5}$

$9 =\frac{9+x}{3}$

$27-9=x$

$18=x$

Thus she traveled 18 km in next 1.5 hours  

Speed = $\frac{Distance}{Time}=\frac{18}{1.5}=12km/hr$

Hence  she need to jog at speed 12 km/hr during the next 1.5 hours.