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Example The probability that a man
aged 60 will live to be 70 is 0.65. What is the probability that
out of 10 men, now 60, at least 7 will live to be 70?
Solution : P = The probability that
a man aged 60 will live to be 70 = 65
\
q = 1 - P = 1 - 0.65 = 0.35
Number of men ( n ) = 10
Probability that at least 7 men will live to 70
= P ( 7 or 8 or 9 or 10 )
Example A and B take turns in throwing
dice. The first to throw 10 is awarded the prize, show that if A
has the first throw, their chance of winning are in the ratio 12
: 11.
Solution : The combinations of throwing 10 from two
dice can be ( 6 + 4 ), ( 4 + 6 ), ( 5 + 5 ).
The number of combination is 3
Total
combinations from two dice = 6
´ 6 = 36
The probability of throwing 10 = 
If A is to win, he should throw 10 in either the first, the third, the fifth, ...
throws. Their respective probabilities
are P1 Q2 P, Q4P1.....
 
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