Practicing Success
A boat can go 30 km downstream and 24 km upstream in 2 hours 27 minutes. Also, it can go 10 km downstream and 4 km upstream in 37 minutes. What is the speed of the boat downstream (km/h)? |
20 24 30 32 |
24 |
D U 30 24 147 min ↓ ↓ ↓ 10 4 37 min ↓ ↓ ↓ ×3 ×3 ×3 ↓ ↓ ↓ 30 12 111 min
in upstream 12 km → in 147 - 111 = 36 min 1 km → 3 min 20 km → 60 min U = 20 km/h
\(\frac{30}{D}\) + \(\frac{24}{20}\) = 147 min \(\frac{30}{D}\) = 147 min - \(\frac{6}{5}\) × 60 \(\frac{30}{D}\) = 75 min D = \(\frac{30}{75}\) × 60 D = 24 km/h |