Answer:
630 km.
Step-by-step explanation:
To obtain the total distance travelled by David, we shall calculate the distance travelled in each, then sum them together.
Case 1:
Speed 1 (S₁) = 65 km / hour
Time 1 (t₁) = 6 hours
Distance 1 (d₁) =?
Speed = Distance /time
S₁ = d₁ / t₁
65 = d₁ / 6
Cross multiply
d₁ = 65 × 6
d₁ = 390 Km
Case 2:
Speed 2 (S₂) = 80 km / hour
Time 2 (t₂ ) = 3 hours
Distance 2 (d₂) =?
Speed = Distance /time
S₂ = d₂ / t₂
80 = d₂ / 3
Cross multiply
d₂ = 80 × 3
d₂ = 240 Km
Finally, we obtained the total distance travelled by David as follow
Distance 1 (d₁) = 390 Km
Distance 2 (d₂) = 240 Km
Total Distance travelled (dₜ) =?
Total distance = distance 1 + distance 2
dₜ = d₁ + d₂
dₜ = 390 + 240
dₜ = 630 km
Therefore, the total distance travelled by David is 630 km