Probability ICSE Class-7th Concise Selina Maths Solutions

Probability ICSE Class-7th Concise Selina mathematics Solutions Chapter-22 . We provide step by step Solutions of Exercise / lesson-22 Probability for ICSE Class-7 Concise Selina Mathematics. Our Solutions contain all type Questions with Exe-22 A and Exe-22 B  to develop skill and confidence. Visit official Website CISCE for detail information about ICSE Board Class-7.

Probability ICSE Class-7th Concise Selina maths Solutions Chapter-22


–: Select Topics :–

 

Exe-22 A,

Exe-22 B,


Concise Mathematics of Exercise – 22 A Probability for ICSE Class-7th Selina  Solutions

Question 1.

A coin is tossed once. Find the probability of
(i) getting a head
(ii) not getting a head
Answer

(i)

Total number of outcomes is Head (H) and Tail (T)

ex, 2

P (Getting a head) = 1/2

(ii)

Total number of outcomes is Head (H) and Tail (T)

ex. 2

P (Not getting a head) = 1/2

Question 2.

A coin is tossed 80 times and the head is obtained 38 times. Now, if a coin tossed once, what will the probability of getting:
(i) a tail
(ii) ahead
Answer

(i) 

∵ Total number of possible outcomes = 80
and, the number of favourable outcomes of getting a tail = 80 − 38 = 42

A coin is tossed 80 times and the head is obtained 38 times. Now, if a coin tossed once, what will the probability of getting a tail

= 42/80=21/40

(ii) 

∵ Total number of possible outcomes = 80
and, the number of favourable outcomes of getting head = 38

∴ Probability of getting a head

A coin is tossed 80 times and the head is obtained 38 times. Now, if a coin tossed once, what will the probability of getting a  head

= (38/80)=(19/40)

Question 3.

A dice is thrown 20 times and the outcomes are noted as shown below:

Outcomes 1 2 3 4 5 6
No. of times 2 3 4 4 3 4

Now a dice is thrown at random, find the probability of getting:

Answer

∵ Total number of outcomes = 20

(i) P (getting 3) = 4/20

=1/5

(ii) A number less than 3 (1, 2) will appear = 2 + 3 = 5 times

∴ Probability = 5/20

=1/4

(iii) A number greater than 3 (4, 5, 6) will appear = 4 + 3 + 4 = 11 times

∴ Probability = 11/20

Question 4.

A survey of 50 boys showed that 21 like tea while 29 dislike it. Out of these boys, one boy is chosen at random. What is the probability that the chosen boy
(i) likes tea
(ii) dislikes tea
Answer

Total number of boys = 50

Number of boys like tea = 21

Number of boys dislike tea = 29

(i) Probability of boys like tea = 21/50

(ii) Probability of boys dislike tea = 29/50

Question 5.

In a cricket match, a batsman hits a boundary 12 times out of 80 balls he plays, further, if he plays one ball more, what will be the probability that:
(i) he hits a boundary
(ii) he does not hit a boundary
Answer

(i) Total number of balls = 80

Hits boundaries = 12 times

∴ P (Hitting a boundary)

= (12/80)=(3/20)

(ii) P (of not hitting a boundary)

= (68/80)=(17/20)

Question 6.

There are 8 marbles in a bag with numbers from 1 to 8 marked on each of them. What is the probability of drawing a marble with number
(i) 3
(ii) 7
Answer

Total number of marbles = 8

(i) Probability (of getting a marble with number 3) = 1/8

(ii) Probability (of getting a marble with number 7) = 1/8

Question 7.

Two coins are tossed simultaneously 100 times and the outcomes are as given below:
Selina Concise Mathematics class 7 ICSE Solutions - Probability-7
If the same pair of coins is tossed again at random, find the probability of getting :
(i) two heads
(ii) exactly one head
(iii) no head.
Answer

(i)

Here, the total number of trials = 100 times

Number of heads got (H, H)

= 21

Probability ICSE Class-7th Concise Selina maths Solutions Chapter-22 img 3

= 21/100

(ii) Total number of trials = 100 times

Number of extract one heads = 55

∴ P(E) =55/100

=11/20

(iii) Total number of trials = 100 times

Number of heads = 24

∴ Probability =24/100

=16/25

Question 8.

A bag contains 4 white and 6 black balls,- all of the same shape and same size. A ball is drawn from the bag without looking into the bag. Find the probability that the ball drawn is :
(i) a black ball
(ii) a white ball
(iii) not a black ball
Answer

Number of white balls = 4

Number of black balls = 6

Number of total balls or possible event = 6 + 4 = 10 balls

(i) Probability (a black ball)

Number of black balls = 6

Number of total balls = 10

∴ Probability =6/10

=3/5

(ii) P (a white ball)

Number of white balls = 4

Number of total balls = 10

∴ Probability =4/10

=2/5

(iii) P (not a black ball)

Probability ICSE Class-7th Concise Selina maths Solutions Chapter-22 img 4

= (4/10) = (2/5)

Question 9.

In a single throw of a dice, find the probability of getting a number:
(i) 4
(ii) 6
(iii) greater than 4

Answer

(i)

Even of getting number 4 = 1

∵ Total outcome number  = 6

∴ Probability =1/6

(ii)

Event of getting number 6 = 1

∵ Total outcome number  = 6

∴ P = 1/6

(iii)

A die has six numbers: 1, 2, 3, 4, 5, 6
∴ Possible number outcomes = 6

a number greater than 4

Numbers of favourable outcomes = greater than four i.e. two number 5 and 6

Probability ICSE Class-7th Concise Selina maths Solutions Chapter-22 img 5

= (2/6)=(1/3)

Question 10.

Hundred identical cards are numbered from 1 to 100. The cards are well shuffled and then a card is drawn. Find the probability that the number on the card drawn is :
(i) 50
(ii) 80
(iii) 40
Answer

(i)

Here, the total number of cards = 100

card is drawn with number = 50

favourable outcomes = 1

Total outcomes  number = 100

∴ P =1/100

(ii)

Here, the total number of cards = 100

card is drawn with number = 80

favourable outcomes = 1

Total outcomes  number = 100

∴ P =1/100

(iii)

Here, the total number of cards = 100

card is drawn with number = 40

favourable outcomes = 1

Total outcomes  number = 100

∴ P =1 /100


Probability of Exe-22 B for ICSE Class-7th Concise mathematics Selina Solutions 

Question 1.

Suppose S is the event that will happen tomorrow and P(S) = 0.03.
(i) State in words, the complementary event S’.
(ii) Find P(S’)
Answer

(i)

Given, P(S) = 0.03

The event will not happens tomorrow.

(ii) 

Given, 

P(S) = 0.03
P(S’) = 1 – P(S)
P(S’) = 1 – 0.03 …………[∵ P(S) + P(S’) = 1]
P(S’) = 0.97

Question 2.

Five Students A, B, C, D and E are competing in a long distance race. Each student’s probability of winning the race is given below:
A → 20 %, B → 22 %, C → 7 %, D → 15% and E → 36 %
(i) Who is most likely to win the race ?
(ii) Who is least likely to win the race ?
(iii) Find the sum of probabilities given.
(iv) Find the probability that either A or D will win the race.
(v) Let S be the event that B will win the race.
(a) Find P(S)
(b) State, in words, the complementary event S’.
(c) Find P(S’)
Answer

Given probabilities of five students A, B, C, D, and E
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. ……….[∵ P(E) = 36% maximun]

(ii)

The least chances of winning the race is of Student C. ……….[∵ P(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%

P(either A or D will win) =(35/100)=(7/20)

(v)

(a) Favourable outcomes that B will win = 22%

P(S) =(22/100)=(11/50)

(b) S’ = B will not win the race.

(c) P(S’) = 1 − P(S)

= 1 – (11/50) = (50-11)/50

=39/50

Question 3.

A Ticket is randomly selected from a basket containing3 green, 4 yellow and 5 blue tickets. Determine the probability of getting:
(i) a green ticket
(ii) a green or yellow ticket.
(iii) an orange ticket.
Answer

Number of green 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 tickets) =3/12

=1/4

(ii) Total Number of green and yellow tickets = 3 + 4

= 7 tickets

P (getting a green or yellow ticket) = 7/12

(iii) Since, Basket contains green, yellow and blue tickets only.

∴ Number or orange tickets = 0

∴ P (getting an orange ticket) = 0/12

=0

Question 4.

Ten cards with numbers 1 to 10 written on them are placed in a bag. A card is chosen from the bag at random. Determine the probability of choosing:
(i) 7
(ii) 9 or 10
(iii) a number greater than 4
(iv) a number less than 6
Answer

Total outcomes number is = 10

ex. 1, 2, 3, 4, 5, 6, 7, 8, 9, 10

(i)

P (of getting a number 7) = 110

(ii)

P (of getting 9 or 10) =2/10

=1/5

(iii)

Numbers greater than 4 are 5, 6, 7, 8, 9 and 10 = 6

P (of getting number greater than 4)
= 6/10

=3/5

(iv)

Numbers less than 6 are 1, 2, 3, 4, 5 = 5

P (of getting a number less than 6)
=5/10

=1/2

Question 5.

A carton contains eight brown and four white eggs. Find the probability that an egg selected at random is :
(i) brown
(ii) white
Answer

Number of brown eggs = 8

Number of white eggs = 4

Total Number of eggs = 8 + 4 = 12

(i) P (of getting a brown eggs) =8/12

=2/3

(ii) P (of getting a white eggs) =4/12

1/3

Question 6.

A box contains 3 yellow, 4 green and 8 blue tickets. A ticket is chosen at random. Find the probability that the ticket is :
(i) yellow
(ii) green
(iii) blue
(iv) red
(v) not yellow
Answer

Number of yellow tickets = 3

Number of green tickets = 4

Number of blue tickets = 3 + 4 + 8 = 15

(i)

P (getting a yellow ticket) =3/15

=1/5

(ii)

P (getting a green ticket) =4/15

(iii)

P (getting a blue ticket) =8/15

(iv)

Since, Basket contains yellow, green and blue tickets only.

∴ Number or red tickets = 0

∴ P (getting an red ticket) =015=0

(v)

Total number of green and blue tickets = 4 + 8 = 12 tickets

P (not getting yellow ticket) = P(getting either green or blue ticket) =12/15

=4/5

Question 7.

The following table shows number of males and number of females of a small locality in different age groups.
If one of the persons, from this locality, is picked at random, what is the probability that
(a) the person picked is a male ?
(b) the person picked is a female ?
(c) the person picked is a female aged 21-50 ?
(d) the person is a male with age up to 50 years?
Answer

∵ Total number of persons = Number of males + Number of females

= 26 + 20 = 46

(a) An event when the person picked is male = 8 + 12 + 6 = 26

∴ Required Probability =26/46

=13/23

(b) An event when the person picked is female = 6 + 10 + 4

∴ Reqired Probability =20/46

=10/23

(c) An event when the person picked is a female aged 21-50 = 10

∴ Required Probaility =10/46

=5/23

(d) An event when the person picked is a male aged up to 50 years = 20

∴ Required probability =20/46

=10/23

 

— End of Probability ICSE Class-7th Concise Solutions :–

Return to – Concise Selina Maths Solutions for ICSE Class -7 


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