Basic facts and techniques of Boats and Streams of Quantitative Aptitude Boats and Streams is a part of the Quantitative aptitude section. This is just a logical extension of motion in a straight line. One or two questions are asked from this chapter in almost every exam. Today I will tell you some important facts and terminologies which will help you to make better understanding about this topic.

Basic facts and techniques of Boats and Streams of Quantitative Aptitude Boats and Streams is a part of the Quantitative aptitude section. This is just a logical extension of motion in a straight line. One or two questions are asked from this chapter in almost every exam. Today I will tell you some important facts and terminologies which will help you to make better understanding about this topic.

Answers (1)


Basic Concept

If direction of boat is same as direction of the stream, then it is known as DOWNSTREAM and if directions are opposite, then it is known as UPSTREAM. Following figure is representing the same:

i.e. if boat is moving with stream then it is known as Downstream and if opposite to stream, then it is Downstream.

Downstream Speed and Upstream Speed

In case of Downstream, as you can see the direction is same, speeds of stream and boat will be added to get Downstream speed.
If Speed of boat in still water = u km/hr Speed of stream = v km/hr, then
Downstream Speed = (u+v) km/hr
Similarly, if I talk about upstream speed, as the direction of boat and stream is opposite, speed of both will be subtracted.
i.e. Upstream Speed = (u-v) km/hr
Study the following figure, notice the directions and try to remember this i.e. If directions are same then speeds will be added and If directions are opposite then speeds will be subtracted

Speeds of Boat and Stream if Downstream and Upstream Speeds are given

Speed of Boat = 1/2 (Downstream Speed + Upstream Speed)
Speed of Stream = 1/2 (Downstream Speed — Upstream Speed)

Problems with Solution

Example1: Speed of boat in still water is 5 km/hr and speed of stream is 1 km/hr. Find the downstream speed and upstream speed.
Solution: Given that, u = 5 km/hr
v = 1 km/hr
Downstream speed = u+ v km/hr ⇒ 5+ 1= 6 km/hr
Upstream speed = u -v km/hr ⇒ 5- 1 = 4 km/hr
Example2: A man takes 3 hours to row a boat 15km downstream of river and 2 hours 30 min to cover a distance of 5 km upstream. Find speed of river or stream.
Solution: We need to find speed of stream from downstream speed and upstream speed. See how I calculate it:
As You know, Speed = Distance/ Time
So, Downstream Speed = (15)/3 = 5 km/hr Upstream Speed = 5/2.5 = 2 km/hr
Now, As i have discussed, Speed of stream = 1/2 (Downstream Speed — Upstream Speed)
⇒Speed of stream = 1/2 (5-2) ⇒3/2 = 1.5 km/hr
Example3: A man can row 7km/hr in still water. If in a river running at 2 km/hr, it takes him 50 minutes to row to his place and back, how far off is the place? *Important Question*
Solution: Given, u = 7km/hr v = 2km/hr From u and v , we can calculate Downstream speed and upstream speed.
Downstream Speed = (u + v) = 7+2 = 9 km/hr Upstream Speed = (u-v) = 7-2 = 5 km/hr
Now, we need to find DISTANCE and time is given,
Time = Distance / Speed
Let required distance = x km
Time taken in downstream + Time taken in upstream = Total Time ⇒ (x/9) + (x/5) = (50)(60)........................ 50 minutes = (50)(60) hrs
⇒Calculating the above equation: x = 2.68km


Relevant Questions

asked 2020-11-22
Time and Work: Techniques and examples with solutions Today I'm going to discuss a very important topic i.e. Time and Work of quantitative aptitude. In almost every exam at least 2-3 question are asked every time. In this chapter, I will tell you about a definite relationship between Time and work and easy method to solve the problems.
asked 2021-01-04
Important Questions of Mensuration: Quantitative Aptitude Mensuration is one the toughest topic of quantitative aptitude section. The only thing is it takes time to analyze the question. Rest is just clarification and formula learning ability of candidate. This chapter is a part of quantitative aptitude section of SSC CGL and SBI PO. Today I will discuss some questions related to basic terms of mensuration.
asked 2020-11-30
Geometry -concepts and properties for SSC CGL Tier-I Geometry is one of the most important topics of Quantitative Aptitude section of SSC CGL exam. It includes various concepts related to lines, angles, triangles, circles, polygons and so on. So, today I will just discuss concept and properties of triangle. Always remember that in Geometry, You need a very basic understanding. Cramming is not gonna help you anywhere.
asked 2020-10-27
Average: Basic Understanding and Properties Today I'm going to start a new topic of quantitative aptitude i.e. Average. It is a very simple topic and just involves simple mathematical calculations. Average concept has various applications. I will discuss its applications in next session. Firstly I will try to make you understand the basics of this topic.
asked 2021-02-25
Give a full and correct answer Why is it important that a sample be random and representative when conducting hypothesis testing? Representative Sample vs. Random Sample: An Overview Economists and researchers seek to reduce sampling bias to near negligible levels when employing statistical analysis. Three basic characteristics in a sample reduce the chances of sampling bias and allow economists to make more confident inferences about a general population from the results obtained from the sample analysis or study: * Such samples must be representative of the chosen population studied. * They must be randomly chosen, meaning that each member of the larger population has an equal chance of being chosen. * They must be large enough so as not to skew the results. The optimal size of the sample group depends on the precise degree of confidence required for making an inference. Representative sampling and random sampling are two techniques used to help ensure data is free of bias. These sampling techniques are not mutually exclusive and, in fact, they are often used in tandem to reduce the degree of sampling error in an analysis and allow for greater confidence in making statistical inferences from the sample in regard to the larger group. Representative Sample A representative sample is a group or set chosen from a larger statistical population or group of factors or instances that adequately replicates the larger group according to whatever characteristic or quality is under study. A representative sample parallels key variables and characteristics of the large society under examination. Some examples include sex, age, education level, socioeconomic status (SES), or marital status. A larger sample size reduced sampling error and increases the likelihood that the sample accurately reflects the target population. Random Sample A random sample is a group or set chosen from a larger population or group of factors of instances in a random manner that allows for each member of the larger group to have an equal chance of being chosen. A random sample is meant to be an unbiased representation of the larger population. It is considered a fair way to select a sample from a larger population since every member of the population has an equal chance of getting selected. Special Considerations: People collecting samples need to ensure that bias is minimized. Representative sampling is one of the key methods of achieving this because such samples replicate as closely as possible elements of the larger population under study. This alone, however, is not enough to make the sampling bias negligible. Combining the random sampling technique with the representative sampling method reduces bias further because no specific member of the representative population has a greater chance of selection into the sample than any other. Summarize this article in 250 words.
asked 2021-03-07
Solved examples of number series in Quantitative aptitude As we know, questions related to number series are very important in Quantitative aptitude section, So, today I’m going to discuss some problems of number series. These are just for your practice. I have already discussed this chapter in previous session i.e. Sequence and Series. Read this article first, then go through these examples.
asked 2021-02-09
Trigonometry is one of the most interesting chapters of Quantitative Aptitude section. Basically, it is a part of SSC syllabus. Today I will tell you the easy method to learn all the basics of trigonometry i.e. Trigonometric Ratios, facts and formulas.
asked 2021-02-26
Divisibility Rules: Quantitative Aptitude Section There are some specific rules by which we can determine the divisor of the given number. Today I will discuss divisibility rules from 2 to 19. Using these rules you can easily determine a divisor of given number, however large it may be. Let me tell you the rules of divisibility from 2 to 19.
asked 2021-02-16
Important questions of Geometry for SSC CGL Tier I In my previous session, I have discussed some concepts related to triangles. Today I will discuss some important questions of Geometry which used to appear in SSC exams. Generally, questions asked from this section are based on properties of various shapes like lines, angles, triangles, rhombus, circles etc.
asked 2021-02-19
Simple or linear Equations: Tricks and Examples. I have already discussed a concept - Quadratic Equations of quantitative aptitude. Today I will discuss some examples of simple equations which have been proved to be a very important topic for various competitive exams. The problems of linear equations can be easily solved by using simple tricks. Lets discuss how.