- Trending Categories
- Data Structure
- Networking
- RDBMS
- Operating System
- Java
- MS Excel
- iOS
- HTML
- CSS
- Android
- Python
- C Programming
- C++
- C#
- MongoDB
- MySQL
- Javascript
- PHP
- Physics
- Chemistry
- Biology
- Mathematics
- English
- Economics
- Psychology
- Social Studies
- Fashion Studies
- Legal Studies

- Selected Reading
- UPSC IAS Exams Notes
- Developer's Best Practices
- Questions and Answers
- Effective Resume Writing
- HR Interview Questions
- Computer Glossary
- Who is Who

# Abdul, while driving to school, computes the average speed for his trip to be $20km/h$. On his return trip along the same route, there is less traffic and the average speed is $30km/h$. What is the average speed for Abdul's trip?

**Given: **

Average speed while driving to school, $v_1=20km/h$

Average speed while returning from school, $v_1=20km/h$

**
**

**To find: **Average speed of Abdul's trip.

**
**

**Solution:**
Suppose, Abdul is driving $x$ kilometre while going to school.

Suppose, the time taken in driving to school be $t_1$, and the time taken in returning from the school be $t_2$.

We know that formula of distance is given as-

$Distance=Speed\times {Time}$

Therefore,

$Time=\frac {Distance}{Speed}$

**1. **Time taken by Abdul's when his average speed is 20km/h.

$t_1=\frac {x}{v_1}$

Putting the given values, we get-

$t_1=\frac {x}{20}$

2. Time taken by Abdul's when his average speed is 30km/h.

$t_2=\frac {x}{v_2}$

Putting the given values, we get-

$t_2=\frac {x}{30}$

Now,

We know that, formula for average speed is given as-

$\text {Average Speed}=\frac {\text {Total distance travelled}}{\text {Total times taken}}$

Substituting the required values, we get-

$\text {Average Speed}=\frac {x+x}{t_1+t_2}$

$\text {Average Speed}=\frac {x+x}{\frac {x}{v_1}+\frac {x}{v_2}}$

$(putting\ the\ value\ of\ t_1\ and\ t_2)$

$\text {Average Speed}=\frac {2x}{\frac {x}{20}+\frac {x}{30}}$

$\text {Average Speed}=\frac {2x}{\frac {3x+2x}{60}}$

$\text {Average Speed}=\frac {2x}{\frac {5x}{60}}$

$\text {Average Speed}=\frac {2x\times {60}}{5x}$

$\text {Average Speed}=\frac {120x}{5x}$

$\text {Average Speed}=24km/h$

Thus, the average speed of Abdul's trip is **24 km/h.**