Then P(A 1)=45, P(A2)=35, P(A3)=25, P(A4)= 15,

The probability that only one of the students' four questions can't be answered correctly is:

P = P(. a 1a2a3a 4)+P(a 1。 A2A3A4)+P(A 1A2。 A3A4)+P(A 1A2A3。 A4)

= 15×35×25× 15+45×25×25× 15+45×35×35× 15+45×35×25×45

= 154625.

(ii) The possible values of ξ are 0, 1, 2, 3, 4,

P(ξ=0)= 15×25×35×45= I have praised it and stepped on it. What's your comment on this answer? Put away comments//high quality or satisfaction or special types or recommended answers dottimewindow.iperformance & window.iperformance.mark ('c _ best',+newdate); Lawyer recommendation service: If your problem is not solved, please describe your problem in detail and provide free professional consultation through Baidu Legal Pro. Other similar questions 20 14-05-20 A class of students got three questions in a math exam. The first question was answered correctly by 38 people, and the second question was answered correctly by 4 1 person. 72011-121A class of 40 students in a math test, 23 people answered the first question correctly, 27 people answered the second question correctly, and 17 people answered both questions correctly. How many questions were asked? 24220 13-05- 12 In a class math exam, * * has 25 multiple-choice questions, each with 4 points. 3620 15-06-23 There are 40 students in a class taking math exams at the same time. Given that the average score of the test paper is 80, how many students fail at most? Four fifths of the students got the first question right, 17/35 got the second question right, and neither of them got it right. On July 7-65,438+05, 2020, 45 students in a class answered the first question correctly, 36 students answered the second question correctly, and 32 students answered two questions at a time. & gt recommended for you: F.context('cmsRight', [{'URL':'/d01373f082025aaf511aa256e9edab64034f1a07? x-BCE-process = image % 2f resize % 2Cm _ lfit % 2Cw _ 450% 2Ch _ 600% 2c limit _ 1% 2f quality % 2Cq _ 85% 2f format % 2Cf _ auto '，' contractId':'A24KA00562 '，}，{ ' URL ':/s？ word = % E6 % AC % A7 % E6 % B4 % B2 % E6 % 9D % AF & sa = searchpromo _ ozb _ zhidao _ tuijian '，' src ':'/3 BF 33 a 87 e 950352 AAF 5 df 4954 143 fbf2b 2 1 18 b6b？ x-BCE-process = image % 2f resize % 2Cm _ lfit % 2Cw _ 450% 2Ch _ 600% 2c limit _ 1% 2f quality % 2Cq _ 85% 2f format % 2Cf _ auto '，' contractId ':' '，}])； The price of electric cars has dropped many times. Is the quality guaranteed? What impact will the "network toilet" have? Is Huaqiang North's second-hand mobile phone reliable? Why is the cost of cancer treatment getting higher and higher? I recommend f.context ('recbrand', [{"img": "\/86D6277F9E2F07083523F69DFB 24B 899A901F20d? x-BCE-process = image % 2f resize % 2Cm _ lfit % 2Cw _ 450% 2Ch _ 600% 2c limit _ 1% 2f quality % 2Cq _ 85% 2f format % 2Cf _ auto "，" url":"/hm.js？ 6859 ce 5a af 00 FB 00387 e 6434 E4 FCC 925 "； var s = document . getelementsbytagname(" script ")[0]； s.parentNode.insertBefore(hm，s)； })(); window . TT = 1720 1 1953 1；