Question

Vasant covers 1/4^th part of distance at 30 km/h, 1/3^rd at 40 km/h and remaining at 20 km/h. Find the average speed.
1. 80/3 kmph
2. 80/9 kmph
3. 37/5 kmph
4. None of the above

Answer 1

Correct Answer - Option 1 : 80/3 kmph

Given:

Vasant covered 1/4^th part with speed = 30 km/h

Vasant covered 1/3^rd part with speed = 40 km/h

Vasant covered remaining part with speed = 20 km/h

Formula used:

Speed = Distance/ Time

Calculation:

Let total time taken be X km

⇒ Total time taken = ((X/ 4)/ 30) + ((X/ 3)/ 40) + ((5X/ 12)/ 20)

⇒ Total time taken = (10X + 10X + 25X)/ 1200

⇒ Total time taken = 45X/ 1200

⇒ Total time taken = 3X/ 80

Average speed = X/(3X/ 80)

⇒ Average speed = 80/ 3 km/h

∴ The average speed is 80/3 km/h