Problems on Average Questions with Solutions PDF

Basic Average Formula and Tricks

For Example : Find the average of all numbers between 5 and 49 which are divisible by 5. 

Solutions : Number are 5, 10, 15, 20, 25, 30, 35, 40, 45, These numbers are divided by 5.

Average Of numbers =	5+10+15+20+25+30+35+40+45	=	225
	9		9

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For Example : The average of 11 numbers is 30. If the average of first six numbers is 17.5 and that of last six is 42.5, then what is the sixth number? 

Solutions:   11 Number's Average is 30 [ Given ]

Sum of 11 Number's is 11 x 30 = 330

Average of first six numbers is 17.5 [ Given ] , so Sum of First 6 Number's is 17.5 x 6 = 105

Average of last six is 42.5 [ Given ] , so Sum of Last 6 Number's is 42.5 x 6 = 255

⇒ Sixth Number = ( Sum of First 6 Number's + Sum of Last 6 Number's ) - Sum of 11 Number's

⇒ Hence the Sixth Number is (105 + 255 ) - 330 = 30

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For Example : A person covers a distance of 50 km from P to Q at a speed of 30 km/hr and returns from Q to P at a speed of 40 km/hr. Find the average speed of person. 

Solutions:   Distance of 50 km from P to Q at a speed of 30 km/hr, Returns from Q to P at a speed of 40 km/hr 

Average Speed =	2 x 30 x 40	=	2400
	30 + 40		70

: : So the Average speed of the person = 34.28 km/hr

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  When new member is added or replaced by other member in the group.

 For Example : The average weight of 8 person's increases by 2.5 kg when a new person comes in place of one of them weighing 65 kg. What might be the weight of the new person?

Solutions:  Total weight increased = (8 x 2.5) kg = 20 kg.

Weight of new person = (65 + 20) kg = 85 kg.

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Average formula for n natural number = (n + 1) / 2

Average formula of n even numbers = (n + 1)

If number value increase or decrease by X, then the average also increase or decrease by A.

In AP ( Arithmetic Progression ), if number of terms are

i) Odd – Average is the middle term.

ii) Even – Average is the average of two middle terms.

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Objective Question On Average Problem

1. The average marks scored by Ganesh in English, Science, Mathematics and History is less than 15 from that scored by him in English, History, Geography and Mathematics. What is the difference of marks in Science and Geography secured by him?

1. A. 40     
2. B. 50      
3. C. 60        Correct Answer
4. D. Data inadequate      

2.  

   
   

   A Mathematics teacher tabulated the marks secured by 35 students of 8th class. The average of their marks was 72. If the marks secured by Beans were written as 36 instead of 86 then find the correct average marks up to two decimal places.

1. A. 73.41     
2. B. 74.3      
3. C. 72.43      
4. D. 73.43        Correct Answer

3.  

   
   

   The average age of a husband and wife was 23 when they were married 5 years ago. The average age of the husband, the wife and a child who was born dining the interval, is 20 years now. How old is the child now?

1. A. 9 months     
2. B. 1 year      
3. C. 3 years      
4. D. 4 years        Correct Answer

4.  

   
   

   The average of four consecutive even numbers is one-fourth of the sum of these numbers. What is the difference between the first and the last number?

1. A. 4     
2. B. 6        Correct Answer
3. C. 2      
4. D. Cannot be determined      

5.  

   
   

   Of the three numbers, the average of the first and the second is greater than the average of the second and the third by 15. What is the difference between the first and the third of the three numbers

1. A. 15       Correct Answer
2. B. 45      
3. C. 60      
4. D. None of these      

6.  

   
   

   The average of 25 results is 18, that of first 12 is 14 and of the last 12 is 17 Thirteenth result is

1. A. 72     
2. B. 78        Correct Answer
3. C. 85      
4. D. 28      

7.  

   
   

   Average age of seven persons in a group is 30 years. The average age of five persons of this group is 31 years.  What is the average age of the other two persons in the group?

1. A. 55 years       Correct Answer
2. B. 26 years      
3. C. 15 years      
4. D. None of these      

8.  

   
   

   Average weight of three boys P, T and R is 54(1/3) kg while the average weight of three boys T, F and G is 53 kg. What is the average weight of P, T, R, F and H

1. A. 53.8 kg     
2. B. 52.4 kg      
3. C. 53.2 kg      
4. D. Data inadequate         Correct Answer

9.  

   
   

   In a class of 52 students the number of boys is two less than the number of girls. Average weight of the boys is 42 kg, while the average weight of all the 52 students is 40 kg. Approximately what is the average weight of the girls?

1. A. 41 kg     
2. B. 29 kg      
3. C. 40 kg      
4. D. 38 Kg        Correct Answer

10.  

    
    

    While calculating the average of a batsman as 36 in 100 matches that he played, one of the score 90 was incorrectly noted as 40. The percentage error is

1. A. 0.6%     
2. B. 1.36%        Correct Answer
3. C. 1.34%      
4. D. 121%       

11.  

    
    

    The average sale of a car dealership was 15 cars per week. After a promotional scheme, the average sale increased to 21 car per week. The percentage increase in the sale of Car was 

1. A. 40%        Correct Answer
2. B. 140%       
3. C. 42(6/7)%      
4. D. 39.33%      

12.  

    
    

    In a class with a certain number of students, if one new student weighing 50 kg is added, then the average weight of the class increased by 1 kg. If one more student weighing 50 kg is added, then the average weight of the class increases by 1.5 kg over the original average. What is the original weight (in kg) of the class?

1. A. 46      
2. B. 42      
3. C. 27      
4. D. 47        Correct Answer

13.  

    
    

    The average marks of a student in 8 subjects are 87. Of these, the highest marks are 2 more than the one next in value. If these two subjects are eliminated, the average mark of the remaining subjects is 85. What is the highest mark obtained by him?

1. A. 94       Correct Answer
2. B. 91      
3. C. 89      
4. D. 96      

MongoDB Find and FindOne Collection and Shell Method

We will perform all the mongoDB Shell collection methods on studentInfo DB. Create studentInfo Database in MongoDB server. Use the below code for creating the DB.

 

Using db.createCollection() method, create collection in database. Command to create studnet collection in studentInfo Database is below 

Insert Some Document in student collection where we can apply the MongoDB Collection Methods to explore further usage. I am Inserting five document in Student Collection.

Mongo Findone Shell Collection Method

Above Image contain the document in student collection. We will use student Collection from studentInfo DB to execute our Find One Mongo Methods. We will use pretty() function at the end of all the collection to get the output in parse format.

• db.collectionName. find()
• db.collectionName. findOne()
• db.collectionName. findAndModify()
• db.collectionName. findOneAndDelete()
• db.collectionName. findOneAndReplace()
• db.collectionName. findOneAndUpdate()

⇛ db.student.find().pretty() :-

This above MongoDB Shell find Query will return all the document present in the Student Collection without filtering anything.

{
        "_id" : ObjectId("5ebeaafd50845b5c0ea8bf54"),
        "id" : 1,
        "name" : "M Kumar",
        "dob" : "2003-04-07",
        "marks" : 54,
        "created_at" : "2017-11-13 23:33:42"
}
{
        "_id" : ObjectId("5ebeaafd50845b5c0ea8bf55"),
        "id" : 2,
        "name" : "MOHAMMED ISHAQ  H",
        "dob" : "2002-06-14",
        "marks" : 67,
        "created_at" : "2016-11-13 23:33:42"
}
{
        "_id" : ObjectId("5ebeaafd50845b5c0ea8bf56"),
        "id" : 3,
        "name" : "ANBUSELVAM S",
        "dob" : "2004-06-18",
        "marks" : 87,
        "created_at" : "2019-11-13 23:33:42"
}
{
        "_id" : ObjectId("5ebeaafd50845b5c0ea8bf57"),
        "id" : 4,
        "name" : "MARTINPRIYADOSS J",
        "dob" : "2004-03-08",
        "marks" : 43,
        "created_at" : "2012-11-13 23:33:42"
}
{
        "_id" : ObjectId("5ebf58376803d36568082c60"),
        "id" : 5,
        "name" : "JAGAN J",
        "dob" : "2003-04-10",
        "marks" : 98,
        "created_at" : "2012-11-13 23:33:42"
}

⇛ db.student.findOneAndDelete({name:"JAGAN J"})

This above query will find the document in which document.name will be equal to "JAGAN J" and it will delete that particular record and return the deleted document.

{
        "_id" : ObjectId("5ebeaafd50845b5c0ea8bf58"),
        "id" : 5,
        "name" : "JAGAN J",
        "dob" : "2003-04-10",
        "marks" : 98,
        "created_at" : "2012-11-13 23:33:42"
}

⇛ db.student.findOne()

{
        "_id" : ObjectId("5ebeaafd50845b5c0ea8bf54"),
        "id" : 1,
        "name" : "M Kumar",
        "dob" : "2003-04-07",
        "marks" : 54,
        "created_at" : "2017-11-13 23:33:42"
}

db.collectionName.findOne() method will return the first matching record from the document collection.

⇛ db.student.find({name:"M Kumar"}).forEach(printjson)

{

        "_id" : ObjectId("5ebeaafd50845b5c0ea8bf54"),
        "id" : 1,
        "name" : "M Kumar",
        "dob" : "2003-04-07",
        "marks" : 54,
        "created_at" : "2017-11-13 23:33:42"
}

⇛ db.student.find({name:"M Kumar"},{name:1,dob:1,marks:1}).pretty()

{
        "_id" : ObjectId("5ebeaafd50845b5c0ea8bf54"),
        "name" : "M Kumar",
        "dob" : "2003-04-07",
        "marks" : 54
}

Note :- Find() shell Collection Method will pull all the collection document fields. If you want some certain collection field then you have to pass the field-name : 1 as the second parameter. Example code is above for reference.

Logical Operator and Filter on FindOne Shell Method

⇛ db.student.findOne({marks :{$lt:50}},{name:1,dob:1})

{
        "_id" : ObjectId("5ebeaafd50845b5c0ea8bf57"),
        "name" : "MARTINPRIYADOSS J",
        "dob" : "2004-03-08"
}

⇛ db.collection.find({$or:[{marks :{$gt:70}},{name:"JAGAN J"}]}).pretty()

{
        "_id" : ObjectId("5ebea4f850845b5c0ea8bf51"),
        "id" : 3,
        "name" : "ANBUSELVAM S",
        "dob" : "2004-06-18",
        "marks" : 87,
        "created_at" : "2019-11-13 23:33:42"
}
{
        "_id" : ObjectId("5ebea4f850845b5c0ea8bf53"),
        "id" : 5,
        "name" : "JAGAN J",
        "dob" : "2003-04-10",
        "marks" : 98,
        "created_at" : "2012-11-13 23:33:42"
}

MongoDB Crud Operation and Mongo DB Crud

MongoDB Crud Operation Basics

Create studentInfo Database in MongoDB server. Use the below code for creating the DB.

Above use studentInfo command will create the DB in MongoDB Server. If studentInfo DB will exist then it will switch to that instead of creating it. To view the created database in the list you must have to create at least one collection in that.

MongoDB provide db.createCollection() method to create collection in database. Command to create studnet collection in studentInfo Database is below 

Press Enter collection will be created in studentInfo Database with the name of student. To view all the collection in the studentInfo Database use below command. Below command will list all the collection present in the studentInfo Database. 

Insert or Create Document in MongoDb Collection

To insert document in the collection in MongoDB Database. We use below two command to insert the document.

• db.collectionName.insertOne()
• db.collectionName.insertMany()

Using above two method we will insert the document in the student Collection of studentInfo Database. 

This below command will insert one document in student Collection.

db.student.insertOne(
   { 
     "id":1,
     "name":"Manoj Kumar",
     "dob":"2003-04-07",
     "marks":54,
     "created_at":"2017-11-13 23:33:42"
   }
)

To Insert many document at a time we have to use db.collectionName.insertMany() method . Below is the code for inserting many document at a time. We can pass all the document as a array.

db.student.insertMany([
   { 
     "id":2,
     "name":"MOHAMMED  H",
     "dob":"2002-06-14",
     "marks":67,
     "created_at":"2016-11-13 23:33:42"
   },
   { 
     "id":3,
     "name":"ANBUSELVAM S",
     "dob":"2004-06-18",
     "marks":87,
     "created_at":"2019-11-13 23:33:42"
   }
 ])

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Fetch Or Retrieve Document from Collection

To retrieve or fetch the document from the MongoDB collection we use db.collectionName.find() method.

• db.student.find() method will fetch all the document from the specified MongoDB collection. This above method will fetch all the document in single line which will not be in readable format.
• db.student.find().pretty() method will fetch and arrange the collection document in some proper readable format. pretty() method will give you the output is below for reference. 
• 

MongoDB Operators and Query Example

We can apply various filter on mongoDB collection document based on certain condition. We can use various operator also for document filter. Below is the query list and condition to demonstrate the filtration.

$eq (=)	$eq will match the value with specified value.
$gt (>)	$gt will check that the value is greater than specified value.
$gte (>=)	$gte will check that the value is greater than equal to specified Value.
$in (IN)	$in will check that specified value is there in range or not.
$nin (NOTIN)	$nin will check that specified value not lies in the range.
$lt (<)	$lt will check that the value is less than the specified value
$lte (=<)	$lte will check that the value is less than the specified value
$ne (!=)	$ne will check whether the value not equal to specified value

$and	Logical AND join multiple query clause and compare multiple clause and return value as True or False.
$not	Logical NOT Check the query expression and return the result.
$nor	Logical NOR join multiple query clause and compare multiple clause
$or	Logical OR  join multiple query clause and compare multiple clause and return value as True or False

Some Query Example using above operator is below for reference with output.

•  db.student.find({marks:{$eq:43}}).pretty()     O/P is below                                                                                             
  

• db.student.find({marks :{$gte:70}}).pretty()  O/P is below                                                                                 
  

• db.student.find({marks :{$in:[54, 87]}}).pretty()  O/P is below                                                                         
  

Query Using AND Logical Operator in MongoDB

• db.student.find({$and :[{name : "JAGAN J"},{marks :98}]}).pretty()                                               {

          "_id" : ObjectId("5ebeaafd50845b5c0ea8bf58"),
          "id" : 5,
          "name" : "JAGAN J",
          "dob" : "2003-04-10",
          "marks" : 98,
          "created_at" : "2012-11-13 23:33:42"
      }

Query Using OR Logical Operator in MongoDB

• db.student.find({$or :[{name:"JAGAN J"},{marks :{$gt:70}}]}).pretty()                                     {

          "_id" : ObjectId("5ebeaafd50845b5c0ea8bf56"),
          "id" : 3,
          "name" : "ANBUSELVAM S",
          "dob" : "2004-06-18",
          "marks" : 87,
          "created_at" : "2019-11-13 23:33:42"
  }
  {
          "_id" : ObjectId("5ebeaafd50845b5c0ea8bf58"),
          "id" : 5,
          "name" : "JAGAN J",
          "dob" : "2003-04-10",
          "marks" : 98,
          "created_at" : "2012-11-13 23:33:42"
  }

Query Using AND Operator as well as OR in MongoDB

• db.student.find({marks :{$lt : 99}, $or :[{marks :{$in:[43,98]}},{name : "JAGAN J"}]}).pretty()                                                                                                                                  {

          "_id" : ObjectId("5ebeaafd50845b5c0ea8bf57"),
          "id" : 4,
          "name" : "MARTINPRIYADOSS J",
          "dob" : "2004-03-08",
          "marks" : 43,
          "created_at" : "2012-11-13 23:33:42"
  }
  {
          "_id" : ObjectId("5ebeaafd50845b5c0ea8bf58"),
          "id" : 5,
          "name" : "JAGAN J",
          "dob" : "2003-04-10",
          "marks" : 98,
          "created_at" : "2012-11-13 23:33:42"
  }

MongoDB Update Query

Update query in MongoDB is done using below method.

• db.collection.updateOne() 
• db.collection.updateMany() 
• db.collection.replaceOne()

Delete Operation In MongoDB

Delete Query in MongoDB is done using below method.

• db.collection.deleteOne() 
• db.collection.deleteMany()