Question

To go home on Christmas Eve, Vinay travels by Bus at 80 km/hr (yes Bangalore bus service is awesome) from office to Bangalore Airport for $(\frac{1}{3}{)}^3$ of the total time. Then he travels by flight at 700 km/hr for next $(\frac{1}{3}{)}^3$ of time to reach Chennai Airport. Then he takes a cab to his house which travels at 120 km/hr (since its midnight). Find his average speed for the entire journey.

• A. 700 km/hr
• B. 100 km/hr
• C. 300 km/hr
• D. 80 km/hr

Answer 1

The correct option is C

300 km/hr

Let's assume the total time in the journey be T hours.

Trip 1

Office to Bangalore Airport

$t_1=\frac{T}{3}$

$s_1=80km/hr$

Distance from office to bangalore airport $d_1=s.t=80$

Trip 2

Bangalore airport to Chennai airport

$t_2=\frac{t}{3}$

$s_2$ = 700 km/hr

distance from Bangalore airport to Chennai airport

$d_2$ = s.t = 700

Trip 3

Chennai Airport to home

$t_2$ = T/3

$s_3$ = 120 km/hr

distance from Chennai Airport to home

$d_3$ = s.t = 120

Average speed = 300 km/hr

Average speed = 300 km/hr