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### STATISTICS(basic concept) NOTES for RRB NTPC EXAM

The words ‘Statistics’ appears to have been derived from the latin word ‘status’ meaning a (political) state. In its origin, Statistic was simply the collect of data on different aspects of the life of the people. Statistics deals with data collected for specific purposes. We can make decisions about the data by analysing and interpreting it. Central line tendency Mean : The mean or average of a number of observation is the sum of the value of all the observation divided by the total number of the observations. It is denoted by the symbol ,  read as x bar Here n is a number of observation. Example-  people were asked about the time in a week they spend in doing social work in their community. They said 10, 7, 13, 20 and 15 hours respectively.Find the mean (or average) time in a week devoted by them in social work. Sol.  The mean =(Sum of all the observations)/(Total number of observations) =(10 + 7 + 13 + 20 + 15)/5=65/5=13  So, the time spent by these 5 people in doing socia

### Quant Study Notes: Probability

Dear Readers, Today we’ll discuss about Probability. This topic is can fetch you marks easily but you need to know the right concepts and types of questions to practice. All about Probability Probability Probability theory deals in random events. The central objects of probability theory are random variables, and events. Event is generally defined as outcome of an experiment. Events can be classified as deterministic or probabilistic (random). Deterministic Event When an experiment is repeated under homogeneous conditions and it produces the same results, then the experiment is known as deterministic experiment.  ☞ For example  if a car runs at a speed of 50 km/hr under uninterrupted condition it will reach a place 100 km distant in 2 hr. Random or Probabilistic Event An experiment when repeated under identical condition does not produce the same result every time but out come is one of the several possible out comes, then such an experiment is known as a probabilistic experi

### Quant Study Notes: Profit and Loss

PROFIT & LOSS Profit and loss are determined by the value of cost price and selling price. Cost price is the price at which an article is purchased and selling price is the price at which article is sold Profit = selling price - Cost price  Loss = Cost price - Selling price  Percentage profit and loss are always calculated on cost price.  If a cost price of m articles is equal to the selling Price of n articles, then Profit percentage  MARKED PRICE Marked price is also known as the list price. It is the price which is marked on the article. Where CP = cost price and MP = marked price DISCOUNT Shopkeepers devise several ways to attract customers (consumers). Sometimes they sell an article at a price lower than its list price (LP)/marked price (MP). Recall that reduction offered by retailer on the list price is called discount. We may recall that Discount = MP - SP Example 1: Marked price of a dining table is Rs 1350. It is sold at Rs. 1188 after allowing certain disc

### Reasoning Study Notes: Machine Input-Output

In machine input-output, the basic problem is the problem of time. You can obviously get the logic if you are not bound by time, but the challenge is to get the logic as quickly as possible and get done with the questions to score more. Here you can learn how to solve machine input by saving your time The general instruction of what a machine input-output question says are: “When a word and number arrangement machine is given an input line words and number, it arranges them following a particular rule. The following is the illustration of input and re-arrangement”   Example: Input: name 37 11 is his 42 Khan 28 Step I: is name 37 11 his 42 Khan 28 Step II: is 42 name 37 11 his Khan 28 Step III: is 42 his name 37 11 Khan 28 Step IV: is 42 his 37 name 11 Khan 28 Step V:  is 42 his 37 Khan name 11 28 Step VI: is 42 his 37 Khan 28 name 11 VIth step is the last step. The last step is the final output the machine. So what has happened in this example of VI Steps? Input is give

### Quant Study Notes: Ratio and proportion

What is Ratio? Ratio is a mathematical term used to compare two similar quantities expressed in the same units. The ratio of two terms ‘x’ and ‘y’ is denoted by x : y. In ratio x : y , we can say that x as the first term or antecedent and y, the second term or consequent. In general, the ratio of a number x to a number y is defined as the quotient of the numbers x and y i.e. x/y.  Example:  The ratio of 25 km to 100 km is 25:100 or 25/100, which is 1:4 or 1/4, where 1 is called the antecedent and 4 the consequent. Note that fractions and ratios are same; the only difference is that ratio is a unit less quantity while fraction is not.  Compound Ratio Ratios are compounded by multiplying together the fractions, which denote them; or by multiplying together the antecedents for a new antecedent, and the consequents for a new consequent. The compound of a : b and c : d is   i.e. ac : bd.  Properties of Ratio: a : b = ma : mb, where m is a constant a : b : c = A : B : C is equivale

### Top Recommended books for Quantitative aptitude and reasoning for placements and competitive exams

Hello Friends, Today  i am providing you a list of best books for your preparation for placements and competitive exams like CAT,XAT,MAT,UPSC,Civil Services,IBPS,PO etc. Below given serial is not the rating of books but just a normal sequence of books (all books are equally good and best for your preparation).