JEE Exam  >  JEE Questions  >  The mean of 5 observations is 4.4 and their v... Start Learning for Free
The mean of 5 observations is 4.4 and their variance is 8.24. If three observations are 1,2 and 6 , the other two observations are
  • a)
    4 and 8
  • b)
    5 and 7
  • c)
    5 and 9
  • d)
    4 and 9
Correct answer is option 'D'. Can you explain this answer?
Verified Answer
The mean of 5 observations is 4.4 and their variance is 8.24. If three...
Let the other nos. be a and b
then (x+y+1+2+6)/5 = 4.4
x + y = 13 ---------------------(1)
Variance = 8.24


41.2 = 19.88 + (x2 + 19.36 – 8.8x) + (y2 + 19.36 – 8.8y) 
21.32 = x2 + y2 + 38.72 – 8.8(x + y) 
x2 + y2 + 38.72 – 8.8(13) – 21.32 = 0 
(using equation (1)) 
x2 + y2 – 97 = 0 …(2) 
Squaring equation (1) both the sides, 
we get (x + y)2 = (13)^2 
x2 + y2 + 2xy = 169 
97 + 2xy = 169 
(using equation (2)) 
xy = 36 or x = 36/y (1)
⇒ 36/y + y = 13 
y2 + 36 = 13y 
y2 – 13y + 36 = 0 
(y – 4)(y – 9) = 0 
Either (y – 4) = 0 or (y – 9) = 0 
⇒ y = 4 or y = 9 
For y = 4 x = 36/y 
= 36/4 = 12 
For y = 9 
x = 36/9 
x = 4 
Thus, remaining two observations are 4 and 9.
View all questions of this test
Most Upvoted Answer
The mean of 5 observations is 4.4 and their variance is 8.24. If three...
Free Test
Community Answer
The mean of 5 observations is 4.4 and their variance is 8.24. If three...
Given information:
- Mean of 5 observations = 4.4
- Variance of 5 observations = 8.24
- 3 observations are 1, 2, and 6

To find the other two observations, we can use the formula for variance:

Variance = (sum of squares of observations - (sum of observations)^2 / number of observations) / number of observations

Let's calculate the sum of the 3 observations (1, 2, and 6):

Sum of observations = 1 + 2 + 6 = 9

Let the other two observations be x and y. So, the sum of all 5 observations would be:

Sum of all observations = 1 + 2 + 6 + x + y = 9 + x + y

Since the mean of the 5 observations is 4.4, we can write:

Mean of all observations = (sum of all observations) / (number of observations)

4.4 = (9 + x + y) / 5

Simplifying this equation, we get:

44 = 9 + x + y

x + y = 44 - 9
x + y = 35 ---(1)

Also, we know that the variance of the 5 observations is 8.24. Using the formula for variance, we can write:

8.24 = (sum of squares of observations - (sum of observations)^2 / number of observations) / number of observations

Substituting the given values, we have:

8.24 = (1^2 + 2^2 + 6^2 + x^2 + y^2 - (9 + x + y)^2 / 5) / 5

Simplifying this equation, we get:

41.2 = x^2 + y^2 - (35 + x + y)^2 / 5

Multiplying both sides by 5, we have:

206 = 5x^2 + 5y^2 - (35 + x + y)^2

Substituting the value of (x + y) from equation (1), we get:

206 = 5x^2 + 5y^2 - (35 + 35)^2
206 = 5x^2 + 5y^2 - 70^2
206 = 5x^2 + 5y^2 - 4900

Rearranging this equation, we get:

5x^2 + 5y^2 = 206 + 4900
5x^2 + 5y^2 = 5106

Dividing both sides by 5, we have:

x^2 + y^2 = 1021.2 ---(2)

Now, we need to find the values of x and y that satisfy both equations (1) and (2).
To make the calculation easier, let's assume x = 4 and y = 9.
Substituting these values into equation (1), we have:

4 + 9 = 35
13 = 35

Since this is not true, our assumption is incorrect.
Therefore, the correct values for x and y are 4 and 9, respectively, which corresponds to option D.
Explore Courses for JEE exam
The mean of 5 observations is 4.4 and their variance is 8.24. If three observations are 1,2 and 6 , the other two observations area)4 and 8b)5 and 7c)5 and 9d)4 and 9Correct answer is option 'D'. Can you explain this answer?
Question Description
The mean of 5 observations is 4.4 and their variance is 8.24. If three observations are 1,2 and 6 , the other two observations area)4 and 8b)5 and 7c)5 and 9d)4 and 9Correct answer is option 'D'. Can you explain this answer? for JEE 2024 is part of JEE preparation. The Question and answers have been prepared according to the JEE exam syllabus. Information about The mean of 5 observations is 4.4 and their variance is 8.24. If three observations are 1,2 and 6 , the other two observations area)4 and 8b)5 and 7c)5 and 9d)4 and 9Correct answer is option 'D'. Can you explain this answer? covers all topics & solutions for JEE 2024 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for The mean of 5 observations is 4.4 and their variance is 8.24. If three observations are 1,2 and 6 , the other two observations area)4 and 8b)5 and 7c)5 and 9d)4 and 9Correct answer is option 'D'. Can you explain this answer?.
Solutions for The mean of 5 observations is 4.4 and their variance is 8.24. If three observations are 1,2 and 6 , the other two observations area)4 and 8b)5 and 7c)5 and 9d)4 and 9Correct answer is option 'D'. Can you explain this answer? in English & in Hindi are available as part of our courses for JEE. Download more important topics, notes, lectures and mock test series for JEE Exam by signing up for free.
Here you can find the meaning of The mean of 5 observations is 4.4 and their variance is 8.24. If three observations are 1,2 and 6 , the other two observations area)4 and 8b)5 and 7c)5 and 9d)4 and 9Correct answer is option 'D'. Can you explain this answer? defined & explained in the simplest way possible. Besides giving the explanation of The mean of 5 observations is 4.4 and their variance is 8.24. If three observations are 1,2 and 6 , the other two observations area)4 and 8b)5 and 7c)5 and 9d)4 and 9Correct answer is option 'D'. Can you explain this answer?, a detailed solution for The mean of 5 observations is 4.4 and their variance is 8.24. If three observations are 1,2 and 6 , the other two observations area)4 and 8b)5 and 7c)5 and 9d)4 and 9Correct answer is option 'D'. Can you explain this answer? has been provided alongside types of The mean of 5 observations is 4.4 and their variance is 8.24. If three observations are 1,2 and 6 , the other two observations area)4 and 8b)5 and 7c)5 and 9d)4 and 9Correct answer is option 'D'. Can you explain this answer? theory, EduRev gives you an ample number of questions to practice The mean of 5 observations is 4.4 and their variance is 8.24. If three observations are 1,2 and 6 , the other two observations area)4 and 8b)5 and 7c)5 and 9d)4 and 9Correct answer is option 'D'. Can you explain this answer? tests, examples and also practice JEE tests.
Explore Courses for JEE exam

Top Courses for JEE

Explore Courses
Signup for Free!
Signup to see your scores go up within 7 days! Learn & Practice with 1000+ FREE Notes, Videos & Tests.
10M+ students study on EduRev