Quantrex Quantrex AcademyJEE · NEET · NDA PYQs with solutions Open app
NDA 2011
Exam
NDA
Year
2011
Subject
Mathematics
Chapter
Statistics

NDA 2011 · Mathematics · Statistics

The mean of 7 observations is 10 and that of 3 observations is 5....

The mean of 7 observations is 10 and that of 3 observations is 5. What is the mean of all the 10 observations?

Options

  1. A1515
  2. B1010
  3. C8.58.5
  4. D7.57.5

Correct answer

C. 8.58.5

Step-by-step solution

 Total of 7 observations =7×10=70 Total of 3 observations =3×5=15 Total of 10 observations =70+15=85∴ Mean of 10 observations =8510=8.5.\begin{aligned} \text{ Total of } 7 \text{ observations } & =7 \times 10=70 \\ \text{ Total of } 3 \text{ observations } & =3 \times 5=15 \\ \text{ Total of } 10 \text{ observations } & =70+15=85 \\ \therefore \quad \text{ Mean of } 10 \text{ observations } & =\frac{85}{10}=8.5.\end{aligned}
Practice Statistics on Quantrex Academy →

More from Statistics

Let two lines of regression be x+y+11=0 and 2x+3y+4=0 for some data. What is the value of… NDA 2026Passage: The frequency distribution of marks obtained by 100 students in a certain… NDA 2026The standard deviation of 100 observations is 10 . If 5 is multiplied to each of the… NDA 2026Passage: The frequency distribution of marks obtained by 100 students in a certain… NDA 2026If the mean of 20 observations, namely x_1,x_2,x_3,…,x_ 20 is 1·414 , then what is the… NDA 2026If the random variable X has mean 3 and standard deviation 5 , then what is the variance… NDA 2026The standard deviation of 100 observations is 10. If 20 is added to each observation… NDA 2025Consider the following statements: I. Mean and variance have the same unit of… NDA 2025Consider the following for the four (04) items that follow: The frequency distribution of… NDA 2025Consider the following for the four (04) items that follow: The frequency distribution of… NDA 2025Consider the following for the two (02) items that follow: The sum and the sum of squares… NDA 2025The arithmetic mean of 100 observations is 50. If 5 is subtracted from each observation… NDA 2025The standard deviation of 100 observations is 10. If 5 is added to each observation and… NDA 2025Consider the following for the two (02) items that follow: The sum and the sum of squares… NDA 2025Consider the following for the four (04) items that follow: The frequency distribution of… NDA 2025The frequency distribution of the marks obtained by students in a Science examination is… NDA 2025 Full Statistics list Statistics JEE Maths PYQsJEE Mathematics PYQs All NDA PYQs