Quandaries
and Queries
Hi. My name is Sohaib. I am a student who has just been promoted to class 9. I came across this problem that I couldn't solve. This question was in the "quadratic equations" chapter. I need your help regarding this problem. Here it is.
" A boat travels 12 km upstream and back in 1 hour 45 minutes. If the speed of the current is 3km/hr throughout, find the speed of the boat in still water, giving your answer correct to 3 decimal places."
I would like to see the working too.
Sohaib.
Hi Sohaib,
Suppose that the speed of the boat in still water is s km/hr, then against the current the boat travels at (s-3) km/hr. The boat travels 12 km at this speed. How long does it take?
With the current the boat travels at (s+3) km/hr. The boat travels 12 km at this speed. How long does it take?
The sum of these two times is 1 3/4 hours. If you add the two times you found above and equate the sum to 1 3/4 you will have a quadratic equation that you can solve for s.
Cheers,
Penny