请教一个小升初英语奥数题 Three girls A,B and C run in a 100 m race.When A finishes,B is 10 mbehind A and when B finishes C is 20 m behind B.How far in metres was C from A when A finished?(Let’s assume all the athletes run at a constant

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请教一个小升初英语奥数题 Three girls A,B and C run in a 100 m race.When A finishes,B is 10 mbehind A and when B finishes C is 20 m behind B.How far in metres was C from A when A finished?(Let’s assume all the athletes run at a constant

请教一个小升初英语奥数题 Three girls A,B and C run in a 100 m race.When A finishes,B is 10 mbehind A and when B finishes C is 20 m behind B.How far in metres was C from A when A finished?(Let’s assume all the athletes run at a constant
请教一个小升初英语奥数题
Three girls A,B and C run in a 100 m race.When A finishes,B is 10 m
behind A and when B finishes C is 20 m behind B.How far in metres was C from A when A finished?(Let’s assume all the athletes run at a constant speed)
适应小学生思维的方法

请教一个小升初英语奥数题 Three girls A,B and C run in a 100 m race.When A finishes,B is 10 mbehind A and when B finishes C is 20 m behind B.How far in metres was C from A when A finished?(Let’s assume all the athletes run at a constant
A:B=10:9 B:C=10:8 A:B:C=100:90:72 A:C=100:72 所以当A跑完100M时C跑了72M 所以A比B多跑100-72=28M

三个女孩A,B和C在100米的跑道上比赛。当A完成的时候,B在A后面10米处,当B完成的时候,C在B后面20米处。问:当A完成的时候C与A相距多少米?(假设所有人的速度都一样)
答案是 30m

30m 就是A在B前面10M C在B后面20M 即C在A后面30M

当A到达终点时,时间为T1,C距A的距离为X。A,B,C的速度分别为Va,Vb,Vc
Va T1=100
Vb T1=100-10
Vc T1=100-X
得Vb=9/10 Va
当B到达终点时,时间为T2
Vb T2=100
Vc T2=100-20
得Vb=5/4 Vc
Vb=9/10 Va
Vb=5/4 Vc

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当A到达终点时,时间为T1,C距A的距离为X。A,B,C的速度分别为Va,Vb,Vc
Va T1=100
Vb T1=100-10
Vc T1=100-X
得Vb=9/10 Va
当B到达终点时,时间为T2
Vb T2=100
Vc T2=100-20
得Vb=5/4 Vc
Vb=9/10 Va
Vb=5/4 Vc
得Vc=18/25 Va
Vc T1=100-X
即18/25 Va T1=100-X
即X=100-18/25 *100=28m
即当A到达终点时,C距A的距离为28m

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