Question

A car travel 30km at a uniform speed of 40km/hour and next 30km at a uniform speed of 20km/hour. Find the average speed.

Answer 1

Answer:

The total timefor the journey is given by

t=d1/v1+d2/v2

= 30/40+ 30/20

=2.25hr.

The average speed is given by

Vavg=d1+d2/t

=30+30/2.25

26.67 km/h

Answer 2

GIVEN:

• A car travel 30 km at a uniform speed of 40 km / hour .

• A car travel next 30 km at a uniform speed of 20 km / hour .

TO FIND:

• The average speed.

SOLUTION:

CASE 1 :

Distance (1) = 30 km

speed = 40 km / hour

As we know that,

speed = Distance/ time

Therefore,Time = Distance/speed

= 30 / 40 hour

Time (1) = 3/4 hour

CASE 2 :

Distance (2) = 30 km

Speed = 20 km / hour

As we know that,

Time = Distance/speed

= 30 /20 hour

Time (2) = 3 / 2 hour

As we know that ,

$\rm \: average \: speed \: = \: \frac{distance \: 1 \: + \: distnce \: 2}{time \: 1 \: + \: time \: 2} \\ \\ \rm \: average \: speed \: = \: \frac{30 \: km \: + \: 30 \: km}{ \frac{3}{4} \: h \: + \: \frac{3}{2} \: h} \\ \\ \rm \: average \: speed \: = \: \frac{60 \: km}{ \frac{(3 + 6) \: h}{4} } \\ \\ \rm \: averge \: speed \: = \: \frac{60 \: km}{ \frac{9}{4} \: h} \\ \\ \rm \: average \: speed \: = \: \frac{60 \: km}{9 \: h} \: \times \: 4 \\ \\ \rm \: average \: speed \: = \: \frac{240 \: km}{9 \: h} \\ \\ \rm \: average \: speed \: = 26.66 \: km \: h ^{ - 1}$

Therefore, Average speed is 26.66 km/hour.