Six billiard balls, numbered 1 through 6, are placed in a box. Three of the balls are red, and three are blue. One ball is to be drawn randomly from the box.
Quantity A
The probability that the ball drawn will be an even numbered red ball
Quantity B
1/2
1, Quantity A is greater.
2, Quantity B is greater.
3, The two quantities are equal.
4, The relationship cannot be determined from the information given.
公布一下正确答案和答案解释吧:
The information given initially in this problem seems on first glance to be quite specific, but in reality says very little. No details are given regarding the distribution of the colors in terms of the numbers; it is possible that the even numbers are all red, or that none of them are. We are asked to compare the probability that the ball drawn will be even numbered and red with the value 1/2. If each even numbered ball happens to be red, then 3 of the 6 balls will satisfy this condition and the probability of drawing on of these balls will be 1/2. However, it is also possible that none of the even numbered balls is red (each could be blue), or perhaps only one or two. In these cases, the probability will be less than 1/2. Since we cannot determine which quantity is larger (either B is larger, or they are equal) the answer must be D.