Class 8 Maths Data Handling Linking Chances to Probability

Linking Chances to Probability

Chances can be converted to probability by finding the chances of occurring of an event against all the possible outcomes.

Experiment

Outcome/Event

Total possible outcomes

Probability (single outcome/total possible outcomes)

Tossing of a coin

1 (Heads)

2 (Heads or Tails)

1/2

Tossing of a coin

1 (Tails)

2 (Heads or Tails)

1/2

Rolling a Dice

1

6 (1,2,3,4,5 or 6)

1/6

Rolling a Dice

3

6 (1,2,3,4,5 or 6)

1/6

Rolling a Dice

6

6 (1,2,3,4,5 or 6)

1/6

 

Problem: When a die is thrown, list the outcomes of an event of getting:

(i) (a) a prime number (b) not a prime number

(ii) (a) a number greater than 5 (b) a number not greater than 5

Solution:

(i)

(a) Outcomes of event of getting a prime number are 2, 3 and 5.

(b) Outcomes of event of not getting a prime number are 1, 4 and 6.

(ii)

(a) Outcome of event of getting a number greater than 5 is 6.

(b) Outcomes of event of not getting a number greater than 5 are 1, 2, 3, 4 and 5.

 

Problem: Numbers 1 to 10 are written on ten separate slips (one number on one slip), kept in a box and mixed well. One slip is chosen from the box without looking into it.

What is the probability of:

(i) getting a number 6.

(ii) getting a number less than 6.

(iii) getting a number greater than 6.

(iv) getting a 1-digit number.

Solution:

(i) Outcome of getting a number 6 from ten separate slips is one.

Therefore, probability of getting a number 6 = 1/10

(ii) Numbers less than 6 are 1, 2, 3, 4 and 5 which are five. So there are 5 outcomes.

Therefore, probability of getting a number less than 6 = 5/10 = 1/2

(iii) Number greater than 6 out of ten that are 7, 8, 9, 10. So there are 4 possible outcomes.

Therefore, probability of getting a number greater than 6 = 4/10 = 2/5

(iv) One digit numbers are 1, 2, 3, 4, 5, 6, 7, 8 and 9 out of ten.

Therefore, probability of getting a 1-digit number = 9/10

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