Selina Concise Class 7 Math Chapter 22 Probability Exercise 22A Solutions
EXERCISE 22A
(1) (i) Total number of possible outcomes = 2
And, the number of favourable out comes = 1
∴ Probability of getting a head = ½
(ii) Total number of possible outcomes = 2
And, the number of favorable out comes = 2 – 1 = 1
∴ Probability of not getting a head = ½
(2) (i) Total number of possible outcomes = 80
And, the number of favourable outcomes = 80 – 38 = 42
∴ Probability of getting a tail = 42/80 = 21/40
(ii) Total number of possible outcomes = 80
And the number of favourable outcomes = 38
∴ Probability of getting head = 38/80 = 19/40
(3) Total number of outcomes = 20
(i) P (getting 3) = 4/20 = 1/5
(ii) P (getting less than 3) = (3+2)/20 = 5/20 = ¼
(iii) P (getting greater than 3) = (4+3+4)/20 = 11/20
(4) Total numbers of boys = 50
Number of boys who like tea = 21
Number of boys who dislike tea = 29
(i) Probability of boys like tea = 21/50
(ii) Probability of boys dislike tea = 29/50
(5) Total number of balls = 80
Hits boundaries = 12 times
(i) P (getting hitting boundary) = 12/80 = 3/20
(ii) P (getting not hitting boundary) = (80-12)/80 = 68/80 = 17/20
(6) The total numbers of marble = 8
(i) P (getting marble with number 3) = 1/8
(ii) P (getting marble with number 8) = 1/8