小学数学趣题,求详解,急!
\u5c0f\u5b66\u6570\u5b66\u8da3\u9898\u8bbe\u516c\u9e21\u6709X\u53ea,\u6bcd\u9e21\u6709Y\u53ea,\u5c0f\u9e21\u6709Z\u53ea,\u5219\u53ef\u5f97\u65b9\u7a0b:
5X\uff0b3Y\uff0bZ\uff0f3\uff1d100 A
X\uff0bY\uff0bZ\uff1d100 B
3A\uff0dB\u5f97
7X\uff0b4Y\uff1d100
\u8fd9\u4e2a\u65b9\u7a0b\u662f\u591a\u89e3\u65b9\u7a0b\uff0c\u7531\u65b9\u7a0b\u53ef\u77e5X\u5fc5\u5b9a\u4e3a\u5076\u6570\uff0c\u8bbeX\uff1d2\uff0c4\uff0c6\uff0c8\uff0c10\uff0c12\uff0c14\uff0c\u5206\u522b\u4ee3\u5165\uff0c\u53ef\u77e5X\uff1d4\uff0c8\uff0c12\u65f6\u7b26\u5408\u65b9\u7a0b\u548c\u5b9e\u9645\u60c5\u51b5\uff0c\u6545\u8fd9\u9898\u6709\u4e09\u89e3\uff0c\u5206\u522b\u662f
X\uff1d4\uff0cY\uff1d18\uff0cZ\uff1d78
X\uff1d8\uff0cY\uff1d11\uff0cZ\uff1d81
X\uff1d12\uff0cY\uff1d4\uff0cZ\uff1d84
2.
\u5927\u513f\u5b504\u4e2a\uff0c\u4e8c\u513f\u5b502\u4e2a\uff0c\u5c0f\u513f\u5b501\u4e2a
\u8bbe\u4e00\u5171\u6709X\u4e2a\u82f9\u679c
\u5927\u513f\u5b50\u5206\u5230\u7684\uff1a0.5x+0.5
\u4e8c\u513f\u5b50\u5206\u5230\u7684\uff1a0.5[x-(0.5x+0.5)]+0.5=0.25x+0.25
\u5c0f\u513f\u5b50\u5206\u5230\u7684\uff1a0.5[x-(0.5x+0.5)-(0.25x+0.25)]+0.5=0.125x+0.125
\u4e09\u4e2a\u513f\u5b50\u5206\u5230\u7684\u82f9\u679c\u52a0\u5728\u4e00\u8d77\u5c31\u662fx
\u53730.5x+0.5+0.25x+0.25+0.125x+0.125=x
\u89e3\u5f97x=7,\u5728\u4ee3\u5165\u5f0f\u4e2d\u5373\u5f97\u6bcf\u4e2a\u513f\u5b50\u5206\u7684\u6570\u76ee
3.
780\u91cc
\u8bbe\u4e3b\u4eba\u7684\u9a6c\u4e00\u5929\u8dd1x\u91cc
\u4e3b\u4eba\u6765\u56de\u7684\u65f6\u95f4\u662f3/4-1/3=5/12
\u5219\u5355\u7a0b\u65f6\u95f4\u4e3a5/24
\u5217\u65b9\u7a0b\uff1a5/24*x=100+5/24*300
\u5f97x=780
4.
\u5927\u548c\u5c1a25\u4e2a \u5c0f\u548c\u5c1a75\u4e2a
5.
16\u53ea \u8bbe\u672a\u77e5\u6570\u975e\u5e38\u597d\u89e3
\u8bbe\u6211\u5bb6\u6709\u9e2d\u5b50X\u53ea \u4e00\u534a\u7684\u4e00\u534a1/2*1/2=1/4
\u5217\u4e2a\u65b9\u7a0b\uff1a 1/4*X+1/2*1/2*X+8=X
\u6700\u540e\u89e3\u5f97\uff1a X=16
\u7531\u4e8e\u662f\u4e24\u679a\u786c\u5e01,\u56e0\u6b64\u51fa\u73b0\u4e00\u6b63\u4e00\u53cd\u7684\u51e0\u7387\u662f50%
\u4e24\u4e2a\u90fd\u662f\u6b63\u9762\u548c\u4e24\u4e2a\u90fd\u662f\u80cc\u9762\u5404\u662f25%.
2X+3(41-X)=100
2X-3X=100-3*41
-X=-23
X=23 则2X=46
则3(41-X)=54
答:高年级46人,低年级54人
用假设法:假设高低年纪各50的话显然不行因为50不能被3整除。如果高年纪48人 低年纪52人也不行因为52不能被3整除。如果高年纪46人 低年纪54人有可能。
46/2=23(组)54/3=18(组)18+23=41(组)41=41
答:高年纪有46人,低年纪54人。
这个可以吧!
高年级X人,低年级是100-X
X/2+(100-X)/3=41
X=46
高年级是46,低年级是54
高年级:X
X/2+(100-X)/3=41组 100-X为低年级人数
X=46
所以高年级 46
低年级54
解:设高年纪X组,低年纪Y组.
2X+3Y=100 X+Y=41
得X=41-Y 2(41-Y)+3Y=100
82-2Y+3Y=100
82-Y=100
Y=18
X=72
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