Selina Concise Class 7 Math Chapter 22 Probability Exercise 22B Solutions
EXERCISE 22B
(1) Given p(S) = 0.03
(i) The event will not snow tomorrow.
(ii) P(S) = 1 – P(S)
⇒ P(S) = 1 – 0.03
⇒ P(S) = 0.97
(2) Given Probabilities of five students A, B, C, D and E such as
P(A) = 20%, P(B) = 22%, P(C) = 7%, P(D) = 15%, P(E) = 36%
(i) The mostly chance of winning the race is of student E = 36% maximum
(ii) The least chances of winning the race is of student C = 7% minimum
(iii) The sum of the probabilities = P(A) + P(B) + P(C) + P(D) + P(E)
= 20% + 22% + 7% + 15% + 36% = 100%
(iv) Favourable outcomes that either A or D will win = 20% + 15% = 35%
(v) (a) Favourable outcomes that B will win = 22%
P(S) = 22/100 = 11/50
(b) S’ = B will not win race.
(c) P(S’) = 1 – P(S)
= 1 – 11/50 = (50 – 11)/50 = 39/50
(3) Number of given tickets = 3
Number of yellow tickets = 4
Number of blue tickets = 5
Total number of tickets = 3 + 4 + 5 = 12
(i) P (getting a green ticket) = 3/12 = ¼
(ii) Total number of green and yellow tickets = 3 + 4 = 7
P (getting a green or yellow ticket) = 7/12
(iii) Number of orange ticket = 0; because the basket contains green, yellow and blue tickets only.
P (getting an orange ticket) = 0/12 = 0
(4) Total number of outcomes = 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 = 10
(i) P (getting a number 7) = 1/10
(ii) P (getting 9 or 10) = 2/10 = 1/5
(iii) Number of greater than 4 = 5, 6, 7, 8, 9, 10 = 6
P (getting number greater than 4) = 6/10 = 3/5
(iv) Number less than 6 = 1, 2, 3, 4, 5 = 5
P (getting a number less than 6) = 5/10 = ½
(5) Number of brown eggs = 8
Number of white eggs = 4
Total number of eggs = 8 + 4 = 12
(i) P (getting a brown egg) = 8/12 = 2/3
(ii) P (getting a white egg) = 4/12 = 1/3