Question

The speed of a boat in still water is 13 km/h and the speed of the stream is 4 km/h. How much more time will it take in going upstream than ingoing downstream a distance of 68 km? (Correct to the nearest minute)

• A. 3 h 30 min
• B. 3 h 50 min
• C. 3 h 34 min
• D. 2 h 55 min

Answer 1

Answer:

C. 3 h 34 min

Speed in still water = 13 km/h
Speed of stream = 4 km/h

Speeds

• Upstream speed = (13 - 4 = 9) km/h

• Downstream speed = (13 + 4 = 17) km/h

  Time for 68 km

• Upstream:
  $\frac{68}{9} \approx 7.56 \text{ hours}$
  

• Downstream:
  $\frac{68}{17} = 4 \text{ hours}$
  

  Difference

• $7.56 - 4 = 3.56 \text{ hours}$
  

Convert 0.56 hours to minutes:
$0.56 \times 60 \approx 34 \text{ minutes}$

Final Answer: 3 hours 34 minutes