[讨论]Solutions Wanted

BBird

1.300 people suffer from A, B and C diseases. People suffering from A disease take 35%, People suffering from B take 45% and people suffering from C take 40%. People suffering from two of the diseases take 10%. How many people who suffer from only one disease?

2.A rectangle inscribed inside a circle that has a radius of 3. If the rectangle is not a square, what range can the rectangle’s circumference be?

3.There are 4 balls with colors in red, white, blue and green separately. If 2 balls are taken out. What is the probability of green ball or blue ball?

4.4 numbers are taken out from 0—9 as telephone numbers. If the first digit of the four-digit telephone number cannot be 0, how many telephone numbers can we have from these numbers?