树状图求概率
\u6811\u72b6\u56fe\u548c\u5217\u8868\u65b9\u6cd5\u6c42\u6982\u7387\u4ec0\u4e48\u65f6\u5019\u7528\u5f53\u7814\u7a76\u7684\u5bf9\u8c61\u51fa\u73b02\u79cd\u60c5\u51b5\u7528\u5217\u8868\u6cd5\uff0c\u5f53\u7814\u7a76\u7684\u5bf9\u8c61\u51fa\u73b02\u4e2a\u7ea7\u4ee5\u4e0a\u65f6\u7528\u6811\u72b6\u56fe\u3002
\uff081\uff09\u5b9e\u9a8c\u7684\u4e24\u4e2a\u6b65\u9aa4\u4e4b\u95f4\u5fc5\u987b\u5177\u6709 \uff08 \uff09\u6027\u3002
\uff082\uff09\u5728\u6bcf\u4e00\u6b65\uff0c\u5404\u79cd\u60c5\u51b5\u51fa\u73b0\u7684\u53ef\u80fd\u6027\u90fd \uff08 \uff09\u3002
1 \u968f\u673a\u6027
2 \u76f8\u540c
图2中吃到虫子的概率是:(1/2)*1+(1/2)*0=1/2
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