Selina Concise Class 7 Math Chapter 22 Probability Exercise 22B Solutions

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


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