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