s.5 maths
2013-09-25 6:39 am
In a bag there are 36 balls numbered 1 to 36 .Two balls are drawn randomly from the bag. Find the probability that the difference of the balls is multiple of 5.
回答 (2)
2013-09-25 6:55 am
✔ 最佳答案
Consider 5 groups of numbers :{ 1 , 6 , 11 , 16 , 21 , 26 , 31 , 36} (8 numbers){ 2 , 7 , 12 , 17 , 22 , 27 , 32} (7 numbers){ 3 , 8 , 13 , 18 , 23 , 28 , 33} (7 numbers){ 4 , 9 , 14 , 19 , 24 , 29 , 34} (7 numbers){ 5 , 10 , 15 , 20 , 25 , 30 , 35} (7 numbers)The required probability= (8C2 + 4(7C2)) / 36C2= 8 / 45
2013-09-28 2:47 am
Consider 5 groups of numbers :
{ 1 , 6 , 11 , 16 , 21 , 26 , 31 , 36} (8 numbers)
{ 2 , 7 , 12 , 17 , 22 , 27 , 32} (7 numbers)
{ 3 , 8 , 13 , 18 , 23 , 28 , 33} (7 numbers)
{ 4 , 9 , 14 , 19 , 24 , 29 , 34} (7 numbers)
{ 5 , 10 , 15 , 20 , 25 , 30 , 35} (7 numbers)
The required probability
= (8C2 + 4(7C2)) / 36C2
= 8 / 45
{ 1 , 6 , 11 , 16 , 21 , 26 , 31 , 36} (8 numbers)
{ 2 , 7 , 12 , 17 , 22 , 27 , 32} (7 numbers)
{ 3 , 8 , 13 , 18 , 23 , 28 , 33} (7 numbers)
{ 4 , 9 , 14 , 19 , 24 , 29 , 34} (7 numbers)
{ 5 , 10 , 15 , 20 , 25 , 30 , 35} (7 numbers)
The required probability
= (8C2 + 4(7C2)) / 36C2
= 8 / 45
收錄日期: 2021-04-21 22:31:59
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https://hk.answers.yahoo.com/question/index?qid=20130924000051KK00212