Q1.
Probability of impossible event is .
(a) 0 (b) 1 (c) 1/2 (d) 2/3
Solution.
(a) 0
Solution
Q2.
Two dice are rolled simutdneously. The probability that they show different faces is .
(a) 2/5 (b) 1/5 (c) 1/6
(d) 5/6
Solution.
n(S) = 62 = 36
n(A) = 30
P(A) = n(A)/n(S)
= 30/36
= 5/6
Solution
Q3.
Five unbiased coins are tossed together. find the probability of getting all heads.
(a) 3/32 (b) 1/32 (c) 1 (d) 0
Solution.
n(A) = 1
n(S) = 25 = 32
P(A) = n(A)/n(S)
= 1/32
Solution
Q4.
A boy contains 12 balls out of which y are white balls. If 3 more white balls are but in the bag, the probabilityof drawing a white ball
will be double than earlier . find y.
(a) 4 (b) 3 (c) 2 (d) 1
Solution.
Let there are y white ball
P2 = 2P1
(y + 3)/15 = 2(y/12)
(y + 3)/15 = y/6
(y + 3)/5 = y/2
2y + 6 = 5y
6 = 5y - 2y
6 = 3y
y = 2
Solution
Q5.
One card is drawn from a well shuffled deck of 52 playing cards. What is the probability of getting a face card
(a) 6/13 (b) 1/26 (c) 1/52 (d) 3/13
Solution.
n(S) = 52
n(A) = 12
P(A) = n(A)/n(S)
= 12/52
= 3/13
Solution
Q6.
A ball is thrown inside the circleof radius r, what is the probability that ball will lie in region P.
(a) 0 (b) 1
(c) 1/3 (d) 2/3
Solution.
=
Area of region P/Whole area (area of circle)
= [(120
o/360) x π r
2]/π r
2 = 1/3
Solution
Q7.
Find S.D of the given data x : 6,6,6,6,--------- upto21 times.
(a) 1 (b) 0 (c) 6 (d) 21
Solution.
(b) 0
Note : Standard deviation is the measurement of dispersion and if data has same value it shows there
is no fluctuation.
Solution
Q8.
Find mean for the given data x : 3,3,3,3,3-----3.
(a) 3 (b) 2 (c) 1 (d) 4
Solution.
(a) 3
Solution
Q9.
The mean of first n natural numbers is 9n/17, find n.
(a) 19 (b) 17 (c) 9 (d) 20
Solution.
Mean of first n natural number is (n + 1)/2
(n + 1)/2 = 9n/17
17n + 17 = 18n
17 = n
Solution
Q10.
If the mean of observation x1 x2 -------xn is 18, then the mean of 2x1, 2x2, 2x3
-------2xn is _____________.
(a) 6 (b) 9 (c) 18 (d) 36
Solution.
(d) 36
Note : Mean has impact of change of origin.
Solution
