Mathematics (NDA/NA SOLVED PAPER 2019 (I) (101 to 120)

Total Questions: 20

11. Two symmetric dice flipped with each dice having two sides painted red, two painted black, one painted yellow and the other painted white. What is the probability that both land on the same colour?

Correct Answer: (c) 5/18
Solution:

12. There are n socks in a drawer, of which 3 socks are red. If 2 of the socks are chosen randomly and the probability that both selected socks are red is 1/2, then what is the value of n?

Correct Answer: (b) 4
Solution:

13. Two cards are chosen at random from a deck of 52 playing cards. What is the probability that both of them have the same value?

Correct Answer: (a) 1/17
Solution:

14. In eight throws of a die, 5 or 6 is considered a success. The mean and standard deviation of total number of successes is respectively given by:

Correct Answer: (b) 8/3, 4/3
Solution:

15. Find the answer of given question?

Correct Answer: (b) 1/6
Solution:

16. Consider the following statements:

1. The algebraic sum of deviations of a set of values from their arithmetic mean is always zero.
2. Arithmetic mean > Median > Mode for a symmetric distribution.
Which of the above statements is/are correct?

Correct Answer: (a) Only 1
Solution:

We know that, the algebraic sum of deviations of a set of values from their arithmetic mean is always zero.

17. Let the correlation coefficient between X and Y be 0.6. Random variables Z and W are defined as Z = X + 5 and W = Y/3. What is the correlation coefficient between Z and W?

Correct Answer: (d) 0.6
Solution:

Since, the correlation coefficient is independent of change of origin and scale. It is given that correlation coefficient between X and Y be 0.6.
So, correlation coefficient between Z and W be 0.6.

18. If all the natural numbers between 1 and 20 are multiplied by 3, then what is the variance of the resulting series?

Correct Answer: (c) 299.25
Solution:

19. What is the probability that an interior point in a circle is closer to the centre than to the circumference?

Correct Answer: (a) 1/4
Solution:

20. If A and B are two events, then what is the probability of occurrence of either event A or event B ?

Correct Answer: (b) P(A ∪ B)
Solution:

If A and B are two events, then the probability of occurrence of either event A or event B is P(A ∪ B).