A
number is chosen at random from 1 – 15 inclusive. Find the probability that it
is a multiple of seven or an even number.
Solution
THIS IS A
NON-MUTUALLY EXCLUSIVE EVENT.
Let
n(S) represent sample space
P(E)
= probability of even number
P(M)
= probability of a multiple of 7
n(S)
= {1, 2, 3, 4, 5, 6, 7, 8, 9,10, 11, 12, 13, 14, 15} = 15
n(E)
= {2, 4, 6, 8, 10, 12, 14} = 7
n(M)
= {7, 14 } = 2
But
14 appears on both categories.
P(E)
= 7/15
P(M)
= 2/15
P(EnM)
= 1/15
………………………….
P(EuM)
= P(E) + P(M) - P(EnM)
P(EuM)
= 7/15 + 2/15 -1/15
= 8/15
= 8/15
∴ P(EuM) = 8/15
TRY THIS………………
A
number is chosen at random from 4 – 30 inclusive. Find the probability that it
is a multiple of 3 or an even number.
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