Today i am going to discuss about Boats and streams problems. Observe the below image and note down in your paper as 3 different pictures. Then those are enough to answer any type of BOATS AND STREAMS problem. So, lets see how it works. First of all, see those three vertical broad lines. They denotes Up stream, Speed in still water, and Down stream. And the two small ones are both same, they are stream speeds. When you want to solve this boats problem, draw these lines and mention their appropriate numbers, given in the problem.
Now, we will take an example problem, to solve.
A boat can travel with a speed of 13 km/hr in still water. If the speed
of the stream is 4 km/hr, find the time taken by the boat to go 68 km
downstream.
now, we will take another example to solve in this method.
Sol : You can see the difference between up(against) and Down (along or with)is 11-5 =6
as we have 2 stream speed lines, 6/2 = 3kmph is the stream speed.
now, subtract 3 from 11 or add 3 to 5 which implies 8 anyways.
hence still water speed is 8kmph.
This may take a while to remember. But with this it is easy to minimize time in our examinations.
NOTE : Here is a note to mention. When the arrow going to down stream, it is a plus. ie you need to add when it is down arrow. And Up arrow.. minus
If you may find difficult to remember plus or minus sequence, one small hint is there. Always up stream is lesser than down stream. UP < DOWN
Here i am giving you some problems. Try solving it out.
1. A motorboat, whose speed in 15 km/hr in still water goes 30 km downstream and comes back in a total of 4 hours 30 minutes. What is the speed of the stream (in km/hr)
2. A man's speed with the current is 15 km/hr and the speed of the current is 2.5 km/hr. The man's speed against the current is?
3. A boat running downstream covers a distance of 16 km in 2 hours while for covering the same distance upstream, it takes 4 hours. What is the speed of the boat in still water?
4. A boat covers a certain distance downstream in 1 hour, while it comes back in 1
hours. If the speed of the stream be 3 kmph, what is the speed of the boat in still water?
5. A man rows to a place 48 km distant and come back in 14 hours. He finds that he can row 4 km with the stream in the same time as 3 km against the stream. The rate of the stream is?
6. A man can row at 5 kmph in still water. If the velocity of current is 1 kmph and it takes him 1 hour to row to a place and come back, how far is the place?
7. The speed of a boat in still water in 15 km/hr and the rate of current is 3 km/hr. The distance traveled downstream in 12 minutes is?
Hope this is useful to you and understood. If there is any doubts, pls find time to post me. I'll try my best to answer you. And also if you find any mistakes, make a note of it too. :) see you
