Correct Answer - Option 4 : 31/4 km per hr.

**Given **

Ram covers 20 kms distance at = 6 km per hr

Next 42 km distance at = 9 km per hr

**Case I.**

Distance = 20 kms

Speed = 6 Kms per hr.

**∴ **Time taken (t_{1}) = 20/6= 10/3 hrs.

**Case II.**

Distance = 42 kms

Speed = 9 km per hr.

**∴ **Time taken (t_{2}) = 42/9 hrs.

Total time = 10/3 + 14/3 = 24/3 = 8 hrs.

**∴ Average speed = Todal Distance/Total time**

⇒ 62/8 km per hr.

**⇒ 31/4 km per hr **