Math moving point in senior high school entrance examination.

1 p, exercise time 8/2=4s q, exercise time 10/ 1= 10s p, first come first.

2 when pcmq is rectangular, cq/cp=5/4. If the time is t, then t/(8-2t)=5/4 t=20/7s.

3 pcmq is a trapezoid (rectangle is a special trapezoid) with an area of (cp+mq)*cm/2 mq=4/5cq cm=3/5cq.

Let t be the moment, and the maximum trapezoidal area formula (upper bottom+lower bottom) * height /2.

That is, find the maximum value of (8-2t+4t/5)*3t/(5*2).

(24t-3.6t 2)/ 10 =- / 10

When the bracket is 0, the quadrilateral area is the largest, which is 40/ 10=4.

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