请教4题GWD数学

sdcar2010

If 60 percent of the passengers with round-trip tickets did not take their cars abroad the ship, then 40% of the passengers with round-trip tickets DID take their cars abroad the ship.  

Let's say there are 100 passengers in total. According to the stimulus, 20 of them have round-trip tickets and their cars. Then from the condition that "60 percent of the passengers with round-trip tickets did not take their cars", you know that 40% of the passengers with round-trip tickets DID take their cars.

So the number of round-trip ticket holders = 20/40% = 50

The answer should be 50%

tracychou114

Q30 一个正方形 ABCD ， E为以1为半径即BC,CD为半径所作的圆，于ABCD中。且因为BE=DE，故E在AC对角线上，
E即为 AC对角线与以C为圆心，1为半径所作的圆的交点。
所求三角形 BCE面积 即为 三角形BEC和三角形BEO面积和（o为正方形中心）
及
（根号2/2）的平方*1/2 + （1-根号2/2）*根号2/2*1/2