问题标题：
一道英文数学难题!火速回答!ClassAandclassBhavethesamenumberofstudents.InclassA,theratioofboystogirlsis3to2.InclassB,thenumberfoboysis200%ofthenumberofgirls.IfonegirlinclassAandoneboyinclassbswit
问题描述：
一道英文数学难题!火速回答!
ClassAandclassBhavethesamenumberofstudents.InclassA,theratioofboystogirlsis3to2.InclassB,thenumberfoboysis200%ofthenumberofgirls.IfonegirlinclassAandoneboyinclassbswitchclasses,theratiosofboystogirlsinbothclasseswillbethesame.Findthenumbersofboysandgirlsinthetwoclasses.Showallyouwork.
希望过程可以短一点
注意是两班！
不是只要一班的！
段志生回答：
LetthenumberofgirlsinclassAbeX.
LetthenumberofboysinclassBbeY.
Initially,X/Y=3/2
Y=3X/2
LetthenumberofgirlsinclassBbex.
LetthenumberofgirlinclassBbey.
Initially,y/x=2
y=2x
X+Y=x+y
X+3X/2=x+2x
5/2X=3x
AfteronegirlinclassAisreplacedbyoneboyinclassB
(X-1)/(Y+1)=(x+1)/(y-1)-->multiplebothsideby(Y+1)(y-1)
(X-1)(y-1)=(x+1)(Y+1)
ExpressyandYintermsofX
(X-1)(2x-1)=(x+1)(3X/2+1)
2Xx-X-2x+1=3/2*Xx+x+3/2*X+1
1/2*Xx-5/2X-3x=0
Since5/2X=3x
1/2*Xx-3x-3x=0
Xx-6x=0
SinceX=6x/5
6x/5*x-6x=0
6x*x-30x=0
x(6x-30)=0
x=0OR6x=30
x=5
y=2xy=10
X=6x/5=6
Y=3X/2=9
过程绝对不应该这么复杂>.
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