(60+50)*2+80=300 kilometers

2

Let the length be x, the width be 3/7x, and x- 12 = 3/7x+ 16.

Solve X=49

It is said that it is 49 meters long and 2 1 meter wide.

Area 1029 m2

three

Rice surplus: 201-2.8 * 30 =117.

1 17 divided by 2.6=45 sets.

four

One-way distance =50* 18=900.

Downhill time: 900/75= 12 minutes.

Average speed: 900 * 2/(18+12) = 60m/min.

five

The diameter of the tablecloth is 0.85+0.15 =1m.

The radius is 0.5m

Table cloth area =3. 14*0.5*0.5=0.785 m2.

Circumference =1* 3.14 = 3.14