If U = {x : x is an integer and 1 ≤ x ≤ 20 }
E1 = {x: x is a multiple of 3}
E2 = {x: x is a multiple of 4} and an integer is picked at random from U, find the probability that it is not in E2
A.
3/4
B.
3/10
C.
1/4
D.
1/20
Correct Answer: 3/4
Explanation
U = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20}
E1 = {3, 6, 9, 12, 15, 18}
E2 = {4, 8, 12, 16, 20}
Probability of E2 = 5/20 i.e Total number inE2/Entire number in set
Probability of set E2 = 1 − 5/20
= 15/20
= 3/4
U = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20}
E1 = {3, 6, 9, 12, 15, 18}
E2 = {4, 8, 12, 16, 20}
Probability of E2 = 5/20 i.e Total number inE2/Entire number in set
Probability of set E2 = 1 − 5/20
= 15/20
= 3/4
