Some students went on a field trip. At a speed of 6 km/h, they travelled by bikes for 2 hours; then at a speed of 2 km/h, they walked for another hour; then they took rest for an hour and had lunch for half an hour; then at a speed of 1 m/s, they walked for an hour to visit a garden; and finally at a speed 4 km/h, they returned home in 3 hours. Their average speed, in k,/h, (rounded off to two places of decimal ) is :

3.48

Distance = Speed × Time

Total Distance = 6 × 2 + 2 × 1 + 1 ×\(\frac{18}{5}\) ×1 + 4 ×3

= \(\frac{148}{5}\)

Total time = 2 + 1 + 1 + 0.5 + 1 + 3 = 8.5

Average speed = \(\frac{148}{5×8.5 }\)

= 3.48 km/h