Email us to get an instant 20% discount on highly effective K-12 Math & English kwizNET Programs!

#### Online Quiz (WorksheetABCD)

Questions Per Quiz = 2 4 6 8 10

### High School Mathematics - 213.5 Combination of Two Events

#### Combination of two Events

1. Union of Events
If A and B are 2 events of sample space S then A U B ( or A+B ) is the event that either A or B or both take place.
2. Intersection of Events
If A and B are 2 events of sample space S then A Ç B (or AB ) is the event that both A and B take place.
3. Mutually Exclusive Events
Two events A and B are said to be mutually exclusive if they cannot occur simultaneously. In such case ( A Ç B) is a { } set.
4. Exhaustive Events
Two events are said to be Exhaustive if A U B = S (sample space)

P( A U B) = P(A) + P(B) - P( A Ç B)

Solved Example

A box contains 36 tickets numbered 1 to 36. One ticket is drawn at random. Find the probability that the number on the ticket is either divisible by 3 or is a perfect square.

Solution
n(S)= 36
Let A be the event that the number is divisible by 3.
A = { 3,6,9,12,15,18,21,24,27,30,33,36 }
n(A) = 12 P(A) = 12/36
Let B be the event that the number on the ticket is a perfect square.
P(B) = { 1,4,9,16,25,36 }
n(B) = 6
P(B) = 6/36
Now A Ç B = { 9, 36}
n( A Ç B )= 2
P( A Ç B ) = 2/36
The required probability is P(A U B)
P(A U B) = P(A) + P(B) - P( A Ç B)
= 12/36 + 6/36 -2/36
= 4/9

 Q 1: There are 100 lottery tickets numbered from 1- 100 . One of them is drawn at random. What is the probability that it is a multiple of 5 or 7?1/511/1008/253/8 Q 2: There are 15 tickets bearing numbers from 1-15 . One ticket is drawn from the bag at random. Find the probability that the number on it is an even number or a multiple of 4.9/111/47/151/3 Q 3: 2 dice are rolled. Find the probability that the sum of the numbers on the uppermost face is an even number or a perfect square.11/187/3119/1812/31 Q 4: In a stationery shop the probability that a person asks for an ink pen is 0.8, the probability that he will ask for a gell pen is 0.7 and the probability that he will ask for both is 0.65. Find the probability that he will ask for either of them.23/3117/2012/197/8 Question 5: This question is available to subscribers only! Question 6: This question is available to subscribers only!