maths-help!!!

Man

2009-02-04 12:37 am

a group of eight numbers contains -3,-1,0,2,2,3,5,5

a)
if all the eight numbers are divided into two groups such that the difference between the products of the elements is 100, determine the elements of products.

b)
a number is then randomly chosen from each of the two groups in (a). Find the probability that their mean is an integer

更新1:

consider five lines of different lengths 2,6,10,14,18 Three of them are chosen at random. what is the probability that the three lines can form a triangle

回答 (1)

[匿名]

2009-02-04 12:56 am

✔ 最佳答案

a)
Let the eight numbers be divided into group A and group B, assume the element 0 is in group A, therefore the product of group A must be equal to 0, implies that the product of group B must be 100 (or -100). From the numbers provided, group B can be (2, 2, 5, 5). And then group A is (-3, -1, 0, 3)

b)
For any two numbers, if there means is an integer, they must be both odd number or both even number.
As group B have two odd numbers and two even numbers, therefore the probability of have an integer mean is 50%
(assume you take -3 from group A, the probability of getting an odd number from group B is 50%. And same as the others)

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