人教版小学数学六年级上册人教版小学数学六年级上册确定起跑线100米决赛400米决赛国际标准田径运动场赛道每条跑道的长度12345678直道(m)直径(m)周长(m)全长(m)相差(m)72.675.1228.08235.9385.9685.96400407.857.8585.9685.9685.9685.9685.9685.9677.6—每条跑道的长度12345678直道(m)直径(m)周长(m)全长(m)相差(m)72.675.177.680.182.685.187.690.1228.08235.93243.78251.63259.48267.33275.18283.0385.9685.9685.9685.9685.9685.9685.9685.96400407.85415.7423.55431.4439.25447.1454.957.857.857.857.857.857.857.85—7.85m7.85m每条跑道的长度12345678直道(m)直径(m)周长(m)全长(m)相差(m)72.675.177.680.182.685.187.690.1228.08235.93243.78251.63259.48267.33275.18283.0385.9685.9685.9685.9685.9685.9685.9685.96400407.85415.7423.55431.4439.25447.1454.957.857.857.857.857.857.857.85—巩固、实践：400米运动场上还有200米的比赛，跑道宽为1.25米。如果跑200米，起跑线又该如何确定呢？确定起跑线
