Question

A car travels 40 km in 30 minutes and the next 40 km
in 40 minutes. Calculate the average speed for the
entire journey
​

Answer 1

Answer:

$\boxed{\bf average \ speed=68.57 kmph}$

Step-by-step explanation:

A car travels 40 km in 30 minutes and the next 40 km  in 40 minutes

Calculate the average speed for the  entire journey.

___________________________________________

distance₁ = 40 km

time₁        = 30 min = 30/60 hour = ¹/₂ hour

distance₂ = 40 km

time₂       = 40 min = 40/60 hour = ²/₃ hour

$average \ speed=\frac{total \ distance}{total \ time}$

$average \ speed=\frac{40+40}{\frac{1}{2}+\frac{2}{3} } \\\\ average \ speed=\frac{80}{\frac{3+4}{6} } \\\\ average \ speed=\frac{80 \times6}{7} \\\\ average \ speed=\frac{480}{7} \\\\ average \ speed=68.57 kmph$

Answer 2

Answer:

78 4/7 km/hour

Step-by-step explanation:

average speed= total distance covered  

                                                       

                                total time taken

                         = 40km+ 40km

                                         

                            30 minutes+ 40 minutes (change to hours after addition)

                         = 80km

                               

                            1 1/6 hours

                         =78 4/7 km/hour