Mathematics NDA/NA SOLVED PAPER 2018 (I) (101 to 120)

Total Questions: 20

11. In a test in Mathematics, 20% of the students obtained ‘‘first class’’. If the data are represented by a pie chart, what is the central angle corresponding to ‘‘first class’’?

Correct Answer: (c) 72°
Solution:

12. The mean and standard deviation of a set of values are 5 and 2 respectively. If 5 is added to each value, then what is the coefficient of variation for the new set of values?

Correct Answer: (b) 20
Solution:

13. A train covers the first 5 km of its journey at a speed of 30 km/h and the next 15 km at a speed of 45 km/h. What is the average speed of the train?

Correct Answer: (d) 40 km/h
Solution:

14. Two fair dice are rolled. What is the probability of getting a sum of 7?

Correct Answer: (b) 1/6
Solution:

15. If A and B are two events such that 2P(A) = 3P(B), where 0< P(A) < P(B) < 1, then which one of the following is correct?

Correct Answer: (b) P(A ∩ B) < P(B|A) < P(A|B)
Solution:

16. A box has ten chits numbered 0, 1, 2, 3,.........., 9. First, one chit is drawn at random and kept aside. From the remaining, a second chit is drawn at random. What is the probability that the second chit drawn is ‘‘9’’ ?

Correct Answer: (a) 1/10
Solution:

17. One bag contains 3 white and 2 black balls, another bag contains 5 white and 3 black balls. If a bag is chosen at random and a ball is drawn from it, what is the change that it is white?

Correct Answer: (b) 49/80
Solution:

18. Consider the following in respect of two events A and B:

I. P(A occurs but not B) = P(A) - P(B) if B ⊂ A
II. P(A alone or B alone occurs) = P(A) = P(B) - P(A ∩ B)
III. P(A ∪ B) = P(A) + P(B) if A and B are mutually exclusive
Which of the above is/are correct?

Correct Answer: (b) I and III
Solution:

19. A committee of three has to be chosen from a group of 4 men and 5 women. If the selection is made at random, what is the probability that exactly two members are men?

Correct Answer: (a) 5/14
Solution:

20. The standard deviation σ of the first N natural numbers can be obtained using which one of the following formulae?

Correct Answer: (b)
Solution: