人教版小學(xué)數(shù)學(xué)六年級(jí)上冊(cè)《確定起跑線》課件

確定起跑線人教版數(shù)學(xué)六年級(jí)（上）2021/6/2712021/6/2722021/6/2732021/6/2742021/6/275132終點(diǎn)線2021/6/2762021/6/2772021/6/27885.96m72.6m1.25m1.25m1.25m2021/6/2792021/6/271085.96m72.6m1.25m1.25m1.25m2021/6/27112021/6/271212345678直徑(m)周長(zhǎng)(m)全長(zhǎng)(m)注：π取3.141592021/6/271385.96m72.6m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）2021/6/271412345678直徑(m)周長(zhǎng)(m)全長(zhǎng)(m)72.6228.08400注：π取3.141592021/6/271585.96m72.6m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）1.25m1.25m2021/6/271612345678直徑(m)周長(zhǎng)(m)全長(zhǎng)(m)72.6228.0840075.1235.93407.85注：π取3.141592021/6/271785.96m72.6m第二道直徑：周長(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）1.25m1.25m75.1m2021/6/271812345678直徑(m)周長(zhǎng)(m)全長(zhǎng)(m)72.6228.0840075.1235.93407.8577.6243.79415.71注：π取3.141592021/6/271985.96m72.6m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)：77.6＋1.25＋1.25=80.1（m）80.1×3.14159≈251.64（m）85.96×2＋251.64=423.56（m）1.25m1.25m77.6m2021/6/272012345678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3.141592021/6/272185.96m72.6m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=82.6（m）82.6×3.14159≈259.50（m）85.96×2＋259.5=431.42（m）2021/6/272212345678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3.141592021/6/272385.96m72.6m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≈267.35（m）85.96×2＋267.35=439.27（m）2021/6/272412345678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3.141592021/6/272585.96m72.6m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（m）85.96×2＋275.2=447.12（m）2021/6/272612345678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3.141592021/6/272785.96m72.6m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）90.1×3.14159≈283.06（m）85.96×2＋283.06=454.98（m）2021/6/272812345678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/7.86m7.857.867.857.867.857.857.862021/6/272912345678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3.141592021/6/2730我不用算出每條跑道的長(zhǎng)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(zhǎng)。圓的周長(zhǎng)是這樣算的：第一道：72.6×π第二道：(72.6＋2.5)×π=72.6π＋2.5π第三道：(75.1＋2.5)×π=75.1π＋2.5π第四道：(77.6＋2.5)×π=77.6π＋2.5π第五道：(80.1＋2.5)×π=80.1π＋2.5π第六道：(82.6＋2.5)×π=82.6π＋2.5π第七道：(85.1＋2.5)×π=85.1π＋2.5π第八道：(87.6＋2.5)×π=87.6π＋2.5π每一條跑道都在上一條跑道的基礎(chǔ)上增加2.5π的長(zhǎng)度。你能算出2.5π是多少米嗎？2021/6/2731終點(diǎn)起點(diǎn)200米的跑道，每條道的長(zhǎng)度都是它們?nèi)L(zhǎng)的一半。第一條：400÷2=200（m）第二條：407.85÷2=203.925（m）第三條：415.71÷2=207.855（m）第四條：423.56÷2=211.78（m）第五條：431.42÷2=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