一只不透明的袋子中有1个白球、1个红球和2个黄球，这些球除颜色不同外其它都相同，搅均后从中任意摸出1个球，摸出黄球可能性是 ．
由一只不透明的袋子中有1个白球、1个红球和2个黄球，即可求得小球的总个数，然后根据概率=所求情况数与总情况数之比，即可求得答案．
解：∵一只不透明的袋子中有1个白球、1个红球和2个黄球，
∴一共有1+1+2=4个球，
∴搅均后从中任意摸出1个球，摸出黄球可能性是：
=
．
故答案为：．
此题考查了概率公式的应用．此题比较简单，解题的关键是注意掌握：概率=所求情况数与总情况数之比．
| 完形填空。 | |||
| Mr. Black works in a hospital (医院). As a good __1__, the people in the town like him. He's often __2__ to the patients (病人) and looks them over carefully. __3__ he's always busy and has little time to rest. One morning Mr Black got to the hospital and saw there was a fat woman in the __4__. He called her into his office and asked, " __5_ , madam?" "It was my birthday yesterday, sir", said the woman. "My husband gave me a __6__. But I couldn't push my way in (挤进) it." " __7__, madam," said Mr. Black, "You must lose some weight (减肥). You'll be able to __8__ your coat, if you do all that I say." "You're __9__, sir, " said the rich woman. " He bought me not a coat, but an expensive __10__." | |||
| ( ) 1. A. doctor ( ) 2. A. bad ( ) 3. A. Or ( ) 4. A. classroom ( ) 5. A. How do you do ( ) 6. A. house ( ) 7. A. It doesn’t matter ( ) 8. A. put ( ) 9. A. right ( ) 10. A . bike | B. farmer B. fine B. But B. waiting r oom B. How are you B. coat B. It’s a pleasure B. wear B. wrong B. bus | C. teacher C. cold C. So C. park C. What's the matter C. shop C. I have no idea C. buy C. easy C. car | D. cleaner D. kind D. Then D. zoo D. How old are you D. present D. It’s my favourite D. wash D. safe D. truck |