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1、確定起跑線一、情景引入100米比賽運(yùn)動(dòng)員起跑情形400米比賽運(yùn)動(dòng)員起跑情形132終點(diǎn)線85.96m72.6m1.25m1.25m1.25m85.96m72.6m1.25m1.25m1.25m二、合作探究每一條跑道具體是由哪幾部分組成的?跑道一圈長(zhǎng)度=2條直道長(zhǎng)度+1個(gè)圓的周長(zhǎng)12345678直徑(m)周長(zhǎng)(m)全長(zhǎng)(m)注:π取3.1415985.96m72.6m第一道直徑:周長(zhǎng):全長(zhǎng):72.6m72.6×3.14159≈228.08(m)85.96×2+228.08=400(m)123456
2、78直徑(m)周長(zhǎng)(m)全長(zhǎng)(m)72.6228.08400注:π取3.1415985.96m72.6m第一道直徑:周長(zhǎng):全長(zhǎng):72.6m228.08m400m第二道直徑:周長(zhǎng):全長(zhǎng):72.6+1.25+1.25=75.1(m)75.1×3.14159≈235.93(m)85.96×2+235.93=407.85(m)1.25m1.25m12345678直徑(m)周長(zhǎng)(m)全長(zhǎng)(m)72.6228.0840075.1235.93407.85注:π取3.1415985.96m72.6m第二道直徑:周
3、長(zhǎng):全長(zhǎng):75.1m235.93m407.85m第三道直徑:周長(zhǎng):全長(zhǎng):75.1+1.25+1.25=77.6(m)77.6×3.14159≈243.79(m)85.96×2+243.79=415.71(m)1.25m1.25m75.1m12345678直徑(m)周長(zhǎng)(m)全長(zhǎng)(m)72.6228.0840075.1235.93407.8577.6243.79415.71注:π取3.1415985.96m72.6m第三道直徑:周長(zhǎng):全長(zhǎng):77.6m243.79m415.71m第四道直徑:周長(zhǎng):全長(zhǎng)
4、:77.6+1.25+1.25=80.1(m)80.1×3.14159≈251.64(m)85.96×2+251.64=423.56(m)1.25m1.25m77.6m12345678直徑(m)周長(zhǎng)(m)全長(zhǎng)(m)72.6228.0840075.1235.93407.8577.6243.79415.7180.1251.64423.56注:π取3.1415985.96m72.6m第四道直徑:周長(zhǎng):全長(zhǎng):80.1m251.64m423.56m第五道直徑:周長(zhǎng):全長(zhǎng):80.1+1.25+1.25=82.
5、6(m)82.6×3.14159≈259.50(m)85.96×2+259.5=431.42(m)12345678直徑(m)周長(zhǎng)(m)全長(zhǎng)(m)72.6228.0840075.1235.93407.8577.6243.79415.7180.1251.64423.5682.6259.5431.42注:π取3.1415985.96m72.6m第五道直徑:周長(zhǎng):全長(zhǎng):82.6m259.5m431.42m第六道直徑:周長(zhǎng):全長(zhǎng):82.6+1.25+1.25=85.1(m)85.1×3.14159≈267.
6、35(m)85.96×2+267.35=439.27(m)12345678直徑(m)周長(zhǎng)(m)全長(zhǎng)(m)72.6228.0840075.1235.93407.8577.6243.79415.7180.1251.64423.5682.6259.5431.4285.1267.35439.27注:π取3.1415985.96m72.6m第六道直徑:周長(zhǎng):全長(zhǎng):85.1m267.35m439.27m第七道直徑:周長(zhǎng):全長(zhǎng):85.1+1.25+1.25=87.6(m)87.6×3.14159≈275.20(
7、m)85.96×2+275.2=447.12(m)12345678直徑(m)周長(zhǎng)(m)全長(zhǎng)(m)72.6228.0840075.1235.93407.8577.6243.79415.7180.1251.64423.5682.6259.5431.4285.1267.35439.2787.6275.2447.12注:π取3.1415985.96m72.6m第七道直徑:周長(zhǎng):全長(zhǎng):87.6m275.2m447.12m第八道直徑:周長(zhǎng):全長(zhǎng):87.6+1.25+1.25=90.1(m)90.1×3.141
8、59≈283.06(m)85.96×2+283.06=454.98(m)12345678直徑(m)周長(zhǎng)(m)全長(zhǎng)(m)72.6228.0840075.1235.93407.8577.6243.79415.7180.1251.64423.5682.6259.5431.4285.1267.35439.2787.6275.2447.1290.1283.06454.98注:π取3.14159各跑道的起跑線應(yīng)該相差多少米?7.85m/7.86m7.857.867.857.867.857.85