Question 2.26
A California study concluded that by following 7 simple health rules a man's life can be extended by 11 years n the average and a woman's life by 7 years. These 7 rules are as follows: no smoking, regular exercise, use alcohol moderately, get 7-8 hours of sleep, maintain proper weight, eat breakfast, and do not eat between meals. In how many ways can a person adopt five of these rules to follow
a) If the person presently violates all 7 rules?
b) If the person never drinks and always eats breakfast?
Solutions:
a) 7C5 = 7! / (5! 2!) = 7x6x5x4x3x2x1/{(5x4x3x2x1)(2x1)} = 42/2 = 21 ways
b) Never drinks and always eats breakfast >> 2 rules are used.
7-2=5 rules left to choose in total
Only violate 3 out of the 5 rules
5C3 = 5!/(3!2!) = 10 ways
Only violate 3 out of the 5 rules
ReplyDelete5C3 = 5!/(3!2!) = 10 ways
is this 3....can u pls explain?
i guess a formula ncr=nC(n-r) is applied. r= male or female(2)
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Deletehow nand y its 3 left only....
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