Tool By Zeal Point

Q. A person travels 120 km at 30 km/h and returns the same 120 km at 20 km/h. Find his average speed.

Formula

Average Speed = Total Distance ÷ Total Time

Solution

First journey:

Distance = 120 km
Speed = 30 km/h

Time = 120 ÷ 30 = 4 hours

Return journey:

Distance = 120 km
Speed = 20 km/h

Time = 120 ÷ 20 = 6 hours

Total

Total Distance = 120 + 120 = 240 km

Total Time = 4 + 6 = 10 hours

Therefore,

$Average Speed = 240 = 24 km/h$

Ans: 24 km/h

Trick - Equal Distance

When the distance is equal: $Average Speed = 2 x y/x + y$

Here, $x = 30, y = 20$

$= 2 \times 30 \times 20/30 + 20 = 1200/50 = 24 km/h$

Equal Distance → Use $2 x y/x + y$

Type 6: Average Speed - Practice Set

Use the trick for equal distances:

Q1. A person travels 60 km at 30 km/h and returns at 20 km/h. Find the average speed.

A. 22 km/h B. 24 km/h C. 25 km/h D. 26 km/h

Q2. A car travels the same distance at 40 km/h and 60 km/h. What is its average speed?

A. 45 km/h B. 48 km/h C. 50 km/h D. 52 km/h

Q3. A train travels from A to B at 50 km/h and returns at 30 km/h. Find the average speed.

A. 35 km/h B. 37.5 km/h C. 40 km/h D. 42 km/h

Q4. A bus covers an equal distance at 45 km/h and 75 km/h. Find its average speed.

A. 50 km/h B. 52.5 km/h C. 56.25 km/h D. 60 km/h

Q5. A person travels equal distances at 20 km/h and 30 km/h. Find the average speed.

A. 22 km/h B. 24 km/h C. 25 km/h D. 26 km/h

Trick

For equal distances:

Example:

For 30 km/h and 20 km/h: