NDA MATHS QUESTION BANK

35. The arithmetic mean of three
    observations is x. If the values of two
    observations are y, z, then what is the
    value of the third observation?
    (a) x (b) 2x – y – z (c) 3x – y – z (d) y +
    z – x


36. What is the weighted mean of the
    first n natural numbers whose weights
    are equal to the squares of the
    corresponding numbers?
    (a) (n + 1)/2 (b) [3n(n + 1]/[2(2n + 1)]
    (c) (n + 1) (2n + 1)/6 (d) n(n + 1)/2


37. Following is the frequency
    distribution of life length in hours of
    100 electric bulbs:

Life
leng
th of
bulb
s (in
hrs)

8.5

-

13.

5

13.

5 -

18.

5

18.

5 -

23.

5

23.

5 -

28.

5

28.

5 -

33.

5

33.

5 -

38.

5

No.
of
bulb
s

7 x 40 y 10 2

If the median of life length is 20 hours,
then what are the missing frequencies
(x, y)?
(a) (28, 13) (b) (23, 18) (c) 31, 10) (d)
(25, 16)

38. The marks scored by two students
    A and B in six subjects are given below:
    A 71 56 45 89 54 44
    B 55 74 83 54 38 52
    Which one of the following statements
    is correct?
    (a) The average scores of A and B are

same but A is consistent (b) The

average scores of A and B are not same

but A is consistent (c) The average

scores of A and B are same but B is

consistent (d) The average scores of A

and B are not same but B is consistent

39. A firm employing 30 workers and
    paying on an average Rs. 500 is
    combined with another firm employing
    20 workers paying on an average Rs.


40. What is the average pay of
    workers of the combined firm?
    (a) Rs. 540 (b) Rs. 550 (c) Rs. 560 (d)
    Rs. 580


41. The arithmetic mean of 10 numbers
    was computed as 7.6. It was later
    discovered that a number 8 was
    wrongly read as 3 during the
    computation. What should be the
    correct mean?
    (a) 7.1 (b) 7.6 (c) 8.1 (d) 8.6


42. Consider the following data

x 1 2 3 4 5

f 3 5 9 - 2

The arithmetic mean of the above

distribution is 2.96.

What is the missing frequency?

(a) 4 (b) 6 (c) 7 (d) 842.

42. The following table shows the
    percentage of male and female coffee
    drinkers and non-coffee drinkers in
    two Towns A and B.

Attribut

es

Town A Town B

Mal

e

Femal

e

Mal

e

Femal

e