Multiple choice

In a river, the ratio of the speed of the stream and the speed of a boat in still water is 3 : 7. Again, the ratio of the speed of the stream to the speed of another boat in still water is 6 : 8. What is the ratio of the speed of the first boat to that of the second boat in still water?

  1. 3 : 4

  2. 7 : 4

  3. 4 : 7

  4. 14 : 15

  5. None of these
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

For the first boat, stream:boat = 3:7, so if stream speed is 3k, boat speed is 7k. For the second boat, stream:boat = 6:8 = 3:4, so if stream speed is 3m, boat speed is 4m. Since the stream is the same, 3k = 3m, meaning k = m. The ratio of boat speeds in still water is 7k:4k = 7:4.

Keep practicing — related questions