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单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,确定起跑线,马郎小学 陈伟,人教版六年级数学上册第四单元,1,3,2,终点线,85.96m,72.6m,1.25m,1.25m,1.25m,85.96m,72.6m,1.25m,1.25m,1.25m,1,2,3,4,5,6,7,8,直径,(m),周长,(m),全长,(m),注：,取,3.14159,85.96m,72.6m,第一道,直径：,周长：,全长：,72.6m,72.63.14159228.08,（,m,）,85.962,228.08=400,（,m,）,1,2,3,4,5,6,7,8,直径,(m),周长,(m),全长,(m),72.6,228.08,400,注：,取,3.14159,85.96m,72.6m,第一道,直径：,周长：,全长：,72.6m,228.08m,400m,第二道,直径：,周长：,全长：,72.6,1.25,1.25=75.1,（,m,）,75.1,3.14159235.93,（,m,）,85.962,235.93,=407.85,（,m,）,1.25m,1.25m,1,2,3,4,5,6,7,8,直径,(m),周长,(m),全长,(m),72.6,228.08,400,75.1,235.93,407.85,注：,取,3.14159,85.96m,72.6m,第二道,直径：,周长：,全长：,75.1m,235.93m,407.85m,第三道,直径：,周长：,全长：,75.1,1.25,1.25=77.6,（,m,）,77.6,3.14159243.79,（,m,）,85.962,243.79,=415.71,（,m,）,1.25m,1.25m,75.1m,1,2,3,4,5,6,7,8,直径,(m),周长,(m),全长,(m),72.6,228.08,400,75.1,235.93,407.85,77.6,243.79,415.71,注：,取,3.14159,85.96m,72.6m,第三道,直径：,周长：,全长：,77.6m,243.79m,415.71m,第四道,直径：,周长：,全长：,77.6,1.25,1.25=80.1,（,m,）,80.1,3.14159251.64,（,m,）,85.962,251.64,=423.56,（,m,）,1.25m,1.25m,77.6m,1,2,3,4,5,6,7,8,直径,(m),周长,(m),全长,(m),72.6,228.08,400,75.1,235.93,407.85,77.6,243.79,415.71,80.1,251.64,423.56,注：,取,3.14159,85.96m,72.6m,第四道,直径：,周长：,全长：,80.1m,251.64m,423.56m,第五道,直径：,周长：,全长：,80.1,1.25,1.25=82.6,（,m,）,82.6,3.14159259.50,（,m,）,85.962,259.5,=431.42,（,m,）,1,2,3,4,5,6,7,8,直径,(m),周长,(m),全长,(m),72.6,228.08,400,75.1,235.93,407.85,77.6,243.79,415.71,80.1,251.64,423.56,82.6,259.5,431.42,注：,取,3.14159,85.96m,72.6m,第五道,直径：,周长：,全长：,82.6m,259.5m,431.42m,第六道,直径：,周长：,全长：,82.6,1.25,1.25=85.1,（,m,）,85.1,3.14159267.35,（,m,）,85.962,267.35,=439.27,（,m,）,1,2,3,4,5,6,7,8,直径,(m),周长,(m),全长,(m),72.6,228.08,400,75.1,235.93,407.85,77.6,243.79,415.71,80.1,251.64,423.56,82.6,259.5,431.42,85.1,267.35,439.27,注：,取,3.14159,85.96m,72.6m,第六道,直径：,周长：,全长：,85.1m,267.35m,439.27m,第七道,直径：,周长：,全长：,85.1,1.25,1.25=87.6,（,m,）,87.6,3.14159275.20,（,m,）,85.962,275.2,=447.12,（,m,）,1,2,3,4,5,6,7,8,直径,(m),周长,(m),全长,(m),72.6,228.08,400,75.1,235.93,407.85,77.6,243.79,415.71,80.1,251.64,423.56,82.6,259.5,431.42,85.1,267.35,439.27,87.6,275.2,447.12,注：,取,3.14159,85.96m,72.6m,第七道,直径：,周长：,全长：,87.6m,275.2m,447.12m,第八道,直径：,周长：,全长：,87.6,1.25,1.25=90.1,（,m,）,90.1,3.14159283.06,（,m,）,85.962,283.06,=454.98,（,m,）,1,2,3,4,5,6,7,8,直径,(m),周长,(m),全长,(m),72.6,228.08,400,75.1,235.93,407.85,77.6,243.79,415.71,80.1,251.64,423.56,82.6,259.5,431.42,85.1,267.35,439.27,87.6,275.2,447.12,90.1,283.06,454.98,注：,取,3.14159,各跑道的起跑线应该相差多少米？,7.85m,/7.86m,7.85,7.86,7.85,7.86,7.85,7.85,7.86,1,2,3,4,5,6,7,8,直径,(m),周长,(m),全长,(m),72.6,228.08,400,75.1,235.93,407.85,77.6,243.79,415.71,80.1,251.64,423.56,82.6,259.5,431.42,85.1,267.35,439.27,87.6,275.2,447.12,90.1,283.06,454.98,注：,取,3.14159,我不用算出每条跑道的长度，也知道它们相差多少米,?,两条直道是一样的，所以只需要看圆的周长。圆的周长是这样算的：,第一道：,72.6,第二道：,(72.6,2.5)=,72.6,2.5,第三道：,(75.1,2.5),=75.1,2.5,第四道：,(77.6,2.5),=77.6,2.5,第五道：,(80.1,2.5),=80.1,2.5,第六道：,(82.6,2.5),=82.6,2.5,第七道：,(85.1,2.5),=85.1,2.5,第八道：,(87.6,2.5),=87.6,2.5,每一条跑道都在上一条跑道的基础上增加,2.5,的长度。你能算出,2.5,是多少米吗？,终点,起点,200,米的跑道，每条道的长度都是它们全长的一半。,第一条：,4002=200,（,m,）,第二条：,407.852=203.925,（,m,）,第三条：,415.712=207.855,（,m,）,第四条：,423.562=211.78,（,m,）,第五条：,431.422=215.71,（,m,）,每条道相差,3.925m,或,3,39m,。所以起跑线应依次提前约,3.925m,。,思考：,200,米跑步比赛，跑道宽为,1.25,米，起跑线应依次提前多少米？,谢谢同学们,的坚持！,
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