Mary jogs 9 km at a speed of 6 km per hour. At what speed would she need to jog during the next 1.5 hours to have an average of 9 km per hour for the entire jogging session ?
A. 9 kmph
B. 10 kmph
C. 12 kmph
D. 14 kmph
Answer: Option C
Solution(By Examveda Team)
Let speed of jogging be x km/hrTotal time taken :
$$\eqalign{ & = \left( {\frac{9}{6}{\text{hrs}} + 1.5{\text{ hrs}}} \right) \cr & = 3{\text{ hrs}} \cr} $$
Total distance covered = $$\left( {9 + 1.5x} \right){\text{ km}}$$
$$\eqalign{ & \therefore \frac{{9 + 1.5x}}{3} = 9 \cr & \Leftrightarrow 9 + 1.5x = 27 \cr & \Leftrightarrow \frac{3}{2}x = 18 \cr & \Leftrightarrow x = \left( {18 \times \frac{2}{3}} \right) \cr & \Leftrightarrow x = 12{\text{ kmph}} \cr} $$
Related Questions on Speed Time and Distance
A. 48 min.
B. 60 min.
C. 42 min.
D. 62 min.
E. 66 min.
A. 262.4 km
B. 260 km
C. 283.33 km
D. 275 km
E. None of these
A. 4 hours
B. 4 hours 30 min.
C. 4 hours 45 min.
D. 5 hours
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