View Full Version : integers and probabilities
demoskopico
02-20-2008, 04:49 AM
If an integer n is to be chosen at random from the integers 1 to 96, inclusive, what is the probability that n(n + 1)(n + 2) will be divisible by 8?
A. 1/4
B. 3/8
C. 1/2
D. 5/8
E. 3/4
Please help
kevin
02-20-2008, 03:18 PM
For this product to be a multiple of 8=2^3, n must be either odd or a multiple of 8. Find the probability of each and then simply add these probabilities, as n cannot satisfy both conditions
demoskopico
02-21-2008, 01:53 AM
For this product to be a multiple of 8=2^3, n must be either odd or a multiple of 8. Find the probability of each and then simply add these probabilities, as n cannot satisfy both conditions
why do you say that? if n is odd we won't have multiples of 8 always. ie n=1, product=1*2*3. same problem with n=3,5,9....
maybe you would have said even: 2*3*4 is amultiple of 8, thus:
prob even= 1/2
prob n+1 is a multiple of 8=12/96
sum=5/8
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