Câu 9. Cho hình bình hành ABCD với O là giao điểm của hai đường chéo. Câu nào sau đây là sai? A.
AB CD 
B.
AD BC 
C.
AO OC 
D.
OD BO

You were told that the amount of time lapsed between consecutive trades on the new york stock exchange followed a normal distribution with a mean of 15 seconds. you were also told that the probability that the time lapsed between two consecutive trades to fall between 16 to 17 seconds was 13%. the probability that the time lapsed between two consecutive trades would fall below 13 seconds was 7%. what is the probability that the time lapsed between two consecutive trades will be between 14 and 15 seconds?

Which one ? is the answer and how to find this answer

How many kilograms of a 5% salt solution and how many kilograms of a 15% salt solution must be mixed together to make 45kg of an 8% salt solution?