Mathmatics NDA/NA Solved Paper 2020-I (51-100)

Total Questions: 50

11. The difference between number of students under Physics and Mathematics is largest for the interval

Read the following information and answer the three items that follow:

Correct Answer: (c) 40 - 50
Solution:


Hence, diffrence is largest for the interval (40-50).

12. Consider the following statements :

Read the following information and answer the three items that follow:
(1) Modal value of the marks in Physics lies in the interval 30 - 40.
(2) Median of the marks in Physics is less than that of marks in Mathematics.
Which of the above statements is/are correct ?

Correct Answer: (a) 1 only
Solution:

(1) Modal value of the marks in Physics is the interval in which maximum number of students got his marks. In the marks interval of (30-40), number of students in Physics is 30, which is largest number of students in any interval.
Hence, modal values of marks in physics is (30-40).
Statements (1) is correct.

13. What is the mean of marks in Physics ?

Read the following information and answer the three items that follow:

Correct Answer: (c) 40.9
Solution:

14. What is the standard deviation of the observations

Correct Answer: (b) 2
Solution:

15. Solve the following equation?

Correct Answer: (d) 200
Solution:

16. What is the probability that February of a leap year selected at random, will have five Sundays ?

Correct Answer: (b) 1/7
Solution:

Number of days in February, when year is a leap year = 29 days = 4 weeks + 1 odd day
4 weeks have 4 sundays.

17. The arithmetic mean of 100 observations is 40, Later, it was found that an observation ‘53’ was wrongly read as ‘83’. What is the correct arithmetic mean?

Correct Answer: (b) 39.7
Solution:

18. A husband and wife appear in an interview for two vacancies for the same post. The probability of the husband’s selection is 1/7 and that of the wife’s selection is 1/5. If the events are independent, then the probability of which one of the following is 11/35 ?

Correct Answer: (a) At least one of them will be selected
Solution:

19. A dealer has a stock of 15 gold coins out of which 6 are counterfeits. A person randomly picks 4 out of the 15 gold coins. What is the probability that all the coins picked will be counterfeits ?

Correct Answer: (a) 1/91
Solution:

20. A committee of 3 is to be formed from a group of 2 boys and 2 girls. What is the probability that the committee consists of 2 boys and 1 girl ?

Correct Answer: (d) 1/2
Solution: