光明小学一、二、三年级共有267人,一年级与二年级人数是7：6，二年级与三年级人数比是5:4，各年级多少人
\u67d0\u5c0f\u5b66\u5171\u6709\u5b66\u751f2400\u4eba,\u5176\u4e2d\u4e00\u5e74\u7ea7\u53606\u5206\u4e4b1,\u4e00\u5e74\u7ea7\u3001\u4e8c\u5e74\u7ea7\u4e0e\u4e09\u5e74\u7ea7\u4eba\u6570\u7684\u6bd4\u662f5\uff1a6\uff1a7\uff0c\u4e8c\u3001\u4e09\u5206\u6790\uff1a
\u4e00\u5e74\u7ea7\u4eba\u6570=2400 x 1/6 =400(\u4eba\uff09
\u4e00\u4e8c\u4e09\u4e09\u4e2a\u5e74\u7ea7\u603b\u4eba\u6570\u770b\u4f5c\u6574\u4f531\uff0c\u603b\u4efd\u6570\u4e3a\uff1a5+6+7=18\u4efd
\u90a3\u4e48\u4e00\u5e74\u7ea7\u5360\u4e09\u4e2a\u5e74\u7ea7\u7684\u4efd\u6570\u4e3a\uff1a5/18
\u56e0\u6b64\uff0c\u4e00\u5e74\u7ea7\u4eba\u6570\u548c\u5360\u4e09\u4e2a\u5e74\u7ea7\u4efd\u6570\u6bd4\uff0c\u6784\u6210\u4e86\u5bf9\u5e94\u5173\u7cfb
\u6839\u636e\u5df2\u77e5\u90e8\u5206\u6c42\u6574\u4f53
\u4e09\u4e2a\u5e74\u7ea7\u603b\u4eba\u6570\u4e3a\uff1a2400 x 1/6 \u00f7 5/\uff085+6+7\uff09
=400 \u00f75/18
=1440\uff08\u4eba\uff09
\u4e8c\u5e74\u7ea7\u4eba\u6570\u4e3a\uff1a1440 x 6/\uff085+6+7\uff09=1440 x 6/18=1440 x1/3=480(\u4eba\uff09
\u4e09\u5e74\u7ea7\u4eba\u6570\u4e3a\uff1a1440 x 7/\uff085+6+7\uff09=1440 x 7/18=560(\u4eba\uff09
\u6216\u8005 1440 - 400 - 480=560\uff08\u4eba\uff09
\u7b54\uff1a\u4e8c\u5e74\u7ea7\u6709480\u4eba\uff0c\u4e09\u5e74\u7ea7\u6709560\u4eba\u3002
\u5e74\u7ea7\u4e0e\u4e8c\u5e74\u7ea7\u4eba\u6570\u7684\u6bd4=7:6=35\uff1a30\uff0c
\u4e8c\u5e74\u7ea7\u4e0e\u4e09\u5e74\u7ea7\u7684\u6bd4=5:4=30:24\uff0c
\u4e09\u4e2a\u5e74\u7ea7\u4eba\u6570\u7684\u6bd4,35:30:24\uff0c
\u7b54\uff1a\u8fd9\u4e09\u4e2a\u5e74\u7ea7\u4eba\u6570\u7684\u6bd4\u662f\uff1a35:30:24\uff0c
5:4 =267x35/89 =267x30/89 =267x24/89
=35:30 =105(人） =90（人） =72（人）
30:24
=35:30:24 答：一年级有105人，二年级有90人，三年级有72人。
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