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S.chand books class 8 maths solution chapter 30 Probability exercise 30

EXERCISE 30


Question 1 

A die is rolled once. What is the probability of rolling.
(i) 3

Sol :

=\dfrac{1}{6}


(ii) 7

Sol :

=\dfrac{0}{6}=0


(iii) an even number

Sol :

=\dfrac{3}{6}=\dfrac{1}{2}


(iv) a prime number ?

Sol :

=\dfrac{1}{2}


Question 2 

Ramesh chooses a date at random in April for a party. Calculate the probability that he chooses.
(i) a saturday

Sol :

 

=\dfrac{4}{30}=\dfrac{2}{15}


(ii) a sunday

Sol :

=\dfrac{4}{30}=\dfrac{2}{15}


(iii) a saturday or a sunday

Sol :

=\dfrac{8}{30}=\dfrac{4}{15}


Question 3 

A normal die is rolled . Calculate the probability that the number on the uppermost face when it stops rolling will be
(i) 5

Sol :

 

=\dfrac{1}{6}


(ii) not 5

Sol :

 

=\dfrac{5}{6}


(iii) an odd number

Sol :

=\dfrac{3}{6}=\dfrac{1}{2}


(iv) a prime number

Sol :

 

=\dfrac{3}{6}=\dfrac{1}{2}


(v) a 3 or a 4

Sol :

=\dfrac{2}{6}=\dfrac{1}{3}


(vi) a 1 or a 2 or a 3 or a 4

Sol :

=\dfrac{4}{6}=\dfrac{2}{3}


(vii) an even prime number

Sol :

=\dfrac{1}{6}


Question 4 

A card is chosen at random from an ordinary deck of playing cards. What is the probability that
(i) a diamond is chosen ?

Sol :

(ii) a king is chosen ?
(iii) a black 4 is chosen ?
(iv) a 7 of hearts is chosen ?


Question 5 

Nine playing cards are numbered 2 to 10. A card is elected from these at random. Calculate the probability that the card will be
(i) an odd number?
(ii) a multiple of 4


Question 6 

This spinner is spun. What is the probability of getting
(i) a 1 ?
(ii) not a 1 ?
(iii) a black 4 is chosen ?
(iv) a 7 of hearts is chosen ?


Question 7

In a game at a fete a pointer is spun. you win the amount of money writtem in the sector where the pointer stops. Each sector is equally likely. Work out the probability that you win.
(i) no money
(ii) 2 rupees
(iii) 6 rupees
(iv) 10 rupees


Question 8 

A spinner is made from a regular octagon. It is labelled with three As , two Bs and three Cs. Each of the sides is equally likely to be resting on the table when it stops spinning. Calculate
(i) P(A resting on the table)
(ii) P(B resting on the table)
(iii) P(not C resting on the table)


Question 9 

A pair of die is thrown. Find the probability of getting a sum of 10 or more . is 5 appears an the first die.
[Hint: Favorable cases are (5,5) and (5,6)]

 


Question 10 

A spinner is marked with numbers from 1 to 100. What is the probabilty of
(i) getting a multiple of 3 ?
(ii) fetting a prime number ?
(iii) not getting a multiple of 2 ?


Question 11 

In a scrabble game, there are small tiles with letters on them that are used to form words .The adjoining table shows the number of tiles for each letter. What is the probability of selecting
(i) O from the full set ?
(ii) Consonant from the full set ?
(iii) A , M or J from the full set ?
(iv) Vowel from the full set ?


Question 12 

A survey of 500 families shows the following results :

Number if girls in the family1230
Number of families40050545

Out of these , one is chosen at random. Find the probability that the chosen family has 2 girls

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