②AD = BC； ③AB‖CD； (4) What is the probability that the quadrilateral ABCD is a parallelogram with any two of ∠ a = ∠ c as the condition?
12 13 34 holds.
14 23 24 is invalid.
Probability = 1/2
2. At the beginning of 2008, there was a snowstorm in the south of China, and the power lines in a certain place were crushed by snow. The maintenance team of the power supply bureau had to go to the suburbs 30 kilometers away for emergency repair. The repairman rides the motorcycle first, 15 minutes later, the repair vehicle is loaded with the required materials and set off. As a result, the two cars arrived at the maintenance point at the same time. It is known that the speed of emergency repair vehicle is 1.5 times that of motorcycle. Find the speed of two cars.
3, known, then the relationship between a and b is ()
A.a = b b . ab = 1 c . a =-b d . ab =- 1
A: A.
There are 20 multiple-choice questions in a knowledge contest. For each question, answer one question correctly and get 10; 3 points will be deducted if the answer is wrong or not. Answer at least a few questions correctly, with a total score of not less than 70 points.
Solution: If you have to answer at least X questions correctly, and the total score is not less than 70 points, then there are (20-x) questions that are wrong or not answered correctly.
According to the meaning of the question, get
Answer: You must answer at least 10 correctly, with a total score of not less than 70 points.