Question

A car moving on a straight road covers one third of the distance with 20 km/hr and the rest with 60 km/hr. The average speed is

• A. 40 km/hr
• B. 80 km/hr
• C.
• D. 36 km/hr

Answer 1

Answer: (D)

36 km/hr

Answer 2

Let total distance travelled = x and total time taken t₁ + t₂ $= \frac { x / 3 } { 20 } + \frac { 2 x / 3 } { 60 }$

∴ Average speed $= \frac { x } { \frac { ( 1 / 3 ) x } { 20 } + \frac { ( 2 / 3 ) x } { 60 } } = \frac { 1 } { \frac { 1 } { 60 } + \frac { 2 } { 180 } }$

=