Concept: 1 Mark
Steps: 1 Mark
Answer: 1 Mark
1km = 1000m
Distance between Ranchi and Bangalore = 420 km= 420 ×1000 = 420000m
Distance between Bangalore and Kolkata = 400 km = 400 ×1000 = 400000m
The total distance travelled by David = 420000 + 400000 = 820000m