Question

A person travels two parts of the total distance in the ratio 2:1 with constant speeds of 30kmph and 40 kmph, respectively. What is the average speed of the journey

Answer 1

Average speed is defined as the ratio of total distance covered by the total time taken.

Given that, a person travels two parts of the total distance in the ratio 2:1.

Let us assume that the distance covered by the person in first part is 2M and 1M in second part.

Also given that, he moved with a constant speeds of 30kmph and 40 kmph, respectively.

Time = Distance/Speed

t1 = 2M/30

t2 = 1M/40

Total time taken = t1 + t2

= 2M/30 + 1M/40

= (8M + 3M)/120

= 11M/120

Total distance covered = 2M + 1M = 3M

Now,

Average speed = 3M/(11M/120)

= (3M × 120)/11M

= 360/11

= 32.72

Therefore, the average speed of the journey is 32.72 km/hr.

Answer 2

GIVEN:

• Total distance travelled in ratio 2 : 1
• Constant speeds 30km/h & 40km/h

TO FIND:

• Average speed

SOLUTION:

Let

The distance travelled in ratio 2 : 1 be 2x & x

30km/h be Speed 1

40km/h be Speed 2

Now,

Using

Time = Distance/Speed

→ t1 = 2x/30

→ t1 = x/15

______________________________

→ t2 = x/40

______________________________

Total time = t1 + t2 = x/15 + x/40 = 11x/120

Total distance = d1 + d2 = 2x + x = 3x

Now,

Time 1 = x/15

Time 2 = x/40

Distance 1 = 2x

Distance 2 = x

Avg speed = Total distance/Total time

→ Avg speed = 3x/11x/120

→ Avg speed = 360/11

Hence , average speed =32.72kmh-¹