Mathematics NDA/NA SOLVED PAPER 2021-II (51 to 100)

Total Questions: 50

41. Consider the following statements :

1. The regression line of y on x is y = 3/4x + 2.
2. The regression line of x on y is x = 3/4y +1/4. Which of the above statements is/are correct?
Two regression lines are given as 3x – 4y + 8 = 0 and 4x - 3y - 1 = 0.

Correct Answer: (c) Both 1 and 2
Solution:

42. Consider the following statements:

1. The coefficient of correlations r is 3/4.
2. The means of x and y are 3 and 4 respectively. Which of the above statements is/are correct?
Two regression lines are given as 3x – 4y + 8 = 0 and 4x - 3y - 1 = 0.

Correct Answer: (a) 1 only
Solution:

43. What is the median?

The marks obtained by 60 students in a certain subject out of 75 are given below:

MarksNumber of Students
15–204
20–255
25–3011
30–356
35–405
40–458
45–509
50–556
55–604
60–652
Correct Answer: (c) 39
Solution:
MarksMidpointfcf
15–2017.544
20–2522.559
25–3027.51120
30–3532.5626
35–4037.5531
40–4542.5839
45–5047.5948
50–5552.5654
55–6057.5458
60–6562.5260

44. What is the mode?

The marks obtained by 60 students in a certain subject out of 75 are given below:

MarksNumber of Students
15–204
20–255
25–3011
30–356
35–405
40–458
45–509
50–556
55–604
60–652
Correct Answer: (b) 27.73
Solution:

45. What is the mean of natural numbers contained in the interval [15, 64]?

Correct Answer: (c) 39.5
Solution:

46. For the set of numbers x, x, x + 2, x + 3, x + 10 where x is a natural number, which of the following is/are correct?

1. Mean > Mode
2. Median > Mean
Select the correct answer using the code given below.

Correct Answer: (a) 1 only
Solution:

47. The mean of 10 observations is 5.5. If each observation is multiplied by 4 and subtracted from 44, then what is the new mean?

Correct Answer: (b) 22
Solution:

48. If g is the geometric mean of 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024, then which one of the following is correct?

Correct Answer: (c) 32 < g < 64
Solution:

49. If the harmonic mean of 60 and x is 48, then what is the value of x?

Correct Answer: (c) 40
Solution:

50. What is the mean deviation of first 10 even natural numbers?

Correct Answer: (a) 5
Solution: