確定起跑線ppt課件

人教版六年級數(shù)學(xué)上冊第四單元,課題：確定起跑線 教學(xué)時間：一課時 單位：木壘縣雀仁鄉(xiāng)中心學(xué)校 姓名：蔡淑英,1,確定起跑線,2,1,3,2,終點線,3,4,5,85.96m,72.6m,1.25m,1.25m,1.25m,6,7,85.96m,72.6m,1.25m,1.25m,1.25m,8,9,注：取3.14159,10,85.96m,72.6m,第一道,直徑：,周長：,全長：,72.6m,72.63.14159228.08（m）,85.962228.08=400（m）,11,72.6,228.08,400,注：取3.14159,12,85.96m,72.6m,第一道,直徑：,周長：,全長：,72.6m,228.08m,400m,第二道,直徑：,周長：,全長：,72.61.251.25=75.1（m）,75.13.14159235.93（m）,85.962235.93=407.85（m）,1.25m,1.25m,13,72.6,228.08,400,75.1,235.93,407.85,注：取3.14159,14,85.96m,72.6m,第二道,直徑：,周長：,全長：,75.1m,235.93m,407.85m,第三道,直徑：,周長：,全長：,75.11.251.25=77.6（m）,77.63.14159243.79（m）,85.962243.79=415.71（m）,1.25m,1.25m,75.1m,15,72.6,228.08,400,75.1,235.93,407.85,77.6,243.79,415.71,注：取3.14159,16,85.96m,72.6m,第三道,直徑：,周長：,全長：,77.6m,243.79m,415.71m,第四道,直徑：,周長：,全長：,77.61.251.25=80.1（m）,80.13.14159251.64（m）,85.962251.64=423.56（m）,1.25m,1.25m,77.6m,17,72.6,228.08,400,75.1,235.93,407.85,77.6,243.79,415.71,80.1,251.64,423.56,注：取3.14159,18,85.96m,72.6m,第四道,直徑：,周長：,全長：,80.1m,251.64m,423.56m,第五道,直徑：,周長：,全長：,80.11.251.25=82.6（m）,82.63.14159259.50（m）,85.962259.5=431.42（m）,19,72.6,228.08,400,75.1,235.93,407.85,77.6,243.79,415.71,80.1,251.64,423.56,82.6,259.5,431.42,注：取3.14159,20,85.96m,72.6m,第五道,直徑：,周長：,全長：,82.6m,259.5m,431.42m,第六道,直徑：,周長：,全長：,82.61.251.25=85.1（m）,85.13.14159267.35（m）,85.962267.35=439.27（m）,21,72.6,228.08,400,75.1,235.93,407.85,77.6,243.79,415.71,80.1,251.64,423.56,82.6,259.5,431.42,85.1,267.35,439.27,注：取3.14159,22,85.96m,72.6m,第六道,直徑：,周長：,全長：,85.1m,267.35m,439.27m,第七道,直徑：,周長：,全長：,85.11.251.25=87.6（m）,87.63.14159275.20（m）,85.962275.2=447.12（m）,23,72.6,228.08,400,75.1,235.93,407.85,77.6,243.79,415.71,80.1,251.64,423.56,82.6,259.5,431.42,85.1,267.35,439.27,87.6,275.2,447.12,注：取3.14159,24,85.96m,72.6m,第七道,直徑：,周長：,全長：,87.6m,275.2m,447.12m,第八道,直徑：,周長：,全長：,87.61.251.25=90.1（m）,90.13.14159283.06（m）,85.962283.06=454.98（m）,25,72.6,228.08,400,75.1,235.93,407.85,77.6,243.79,415.71,80.1,251.64,423.56,82.6,259.5,431.42,85.1,267.35,439.27,87.6,275.2,447.12,90.1,283.06,454.98,注：取3.14159,各跑道的起跑線應(yīng)該相差多少米？,7.85m,/ 7.86m,7.85,7.86,7.85,7.86,7.85,7.85,7.86,26,72.6,228.08,400,75.1,235.93,407.85,77.6,243.79,415.71,80.1,251.64,423.56,82.6,259.5,431.42,85.1,267.35,439.27,87.6,275.2,447.12,90.1,283.06,454.98,注：取3.14159,27,我不用算出每條跑道的長度，也知道它們相差多少米?,兩條直道是一樣的，所以只需要看圓的周長。圓的周長是這樣算的：,第一道：72.6,第二道：(72.62.5) = 72.62.5,第三道：(75.12.5) = 75.12.5,第四道：(77.62.5) = 77.62.5,第五道：(80.12.5) = 80.12.5,第六道：(82.62.5) = 82.62.5,第七道：(85.12.5) = 85.12.5,第八道：(87.62.5) = 87.62.5,每一條跑道都在上一條跑道的基礎(chǔ)上增加2.5的長度。你能算出2.5是多少米嗎？,28,終點,起點,200米的跑道，每條道的長度都是它們?nèi)L的一半。,第一條：4002=200（m）,第二條：407.852=203.925（m）,第三條：415.712=207.855（m）,第四條：423.562=211.78（m）,第五條：431.422=215.71（m）,每條道相差3.925m或3,39m。所以起跑線應(yīng)依次提前約3.925m。,思考：200米跑步比賽，跑道寬為1.25米，起跑線應(yīng)依次提前多少米？,29,本節(jié)課你有收獲嗎？ 說說與大家分享一下吧！,30,