NDA MATHS QUESTION BANK

12. The mean of a set of observations is
    ̅. If each observation is divided by,
    α≠0, and then is increased by 10, then
    the mean of the new set is:

(a) ̅^ (b)^ ̅^ (c)^ ̅^ (d) α ̅+10

13. The distributions of X and Y with
    total number of observations 36, 64
    and mean 4, 3 respectively are
    combined. What is the mean of the
    resulting distribution X+Y?
    (a) 3.26 (b) 3.32 (c) 3.36 (d) 3.42


14. Directions (Qs. 1-2) The following
    table gives the frequency distribution
    of life length in hours of 100 electric
    bulbs having median life 20 h

Life of bulbs (in

hours)

Number of bulbs

8 - 13 7

13 - 18 X

18 - 23 40

23 - 28 Y

28 - 33 10

33 - 38 2

1. What is the missing frequency x?
   (a) 31 (b) 27 (c) 24 (d) 14


2. What is the missing frequency y?
   (a) 27 (b) 24 (c) 14 (d) 11


3. The mean of n items is ̅. If the first
   term is increased by 1, second by 2 and
   so on, then the new mean is:

(a) ̅+n (b) ̅ (c) ̅ (d) None

of these

16. Directions (Qs. 1 to 3) The
    frequency distribution of life of 90 TV
    tubes whose median life is 17 months
    is as follows:

Life of TV tubes

(in Months)

No. of TV tubes

0 - 5 3

5 - 10 12

10 - 15 X

15 - 20 35

20 - 25 Y

25 - 30 4

1. What is the lower limit of the median
   class?
   (a) 10 (b) 15 (c) 20 (d) 25


2. What is the missing frequency y?
   (a) 20 (b) 16 (c) 15 (d) 12


3. What is the cumulative frequency of
   the modal class?
   (a) 31 (b) 35 (c) 66 (d) Cant be
   determined


4. Consider the following statements
   in respect of a histogram
   I. The histogram consists of vertical
   rectangular bars with a common base
   such that there is no gap between
   consecutive bars.
   II. The height of the rectangle is
   determined by the frequency of the
   class it represents.
   Which of the statements given above
   is/are correct?
   (a) I only (b) II only (c) Both I and II
   (d) Neither I nor II