A student walked 6 km from his house to reach the metro station, then boarded a metro that has an average speed of 60km/h, and reached the destination. It took 3 hours for the entire journey. If the average speed of the entire journey is 32 km/h, then the speed of walking is ______.

4 km/h

Average speed of whole journey = 32 km/h

Time taken = 3 hours

Total distance = 32 × 3 = 96 km

Average speed of metro  = 60 km/h

Let time taken by metro = t hours

So , Distance = 60 × t = 60t km

According to question ,

6 + 60 × t = 96

 60x = 96 – 6

 60x = 90

 x = \(\frac{90}{60}\)

 x = 1.5 hrs

Time taken to cover 6 km distance = 3 – 1.5 = 1.5 hrs

Walking speed  = \(\frac{Distance}{Time}\)

= \(\frac{6}{1.5}\) = 4 km/hr

So , Average speed of walking is 4 km/hr