Wheel rolling 1 lap, car forward: 8π decimeter,

Rolling for 800 times, the length of this tunnel = 8x π x800 ≈ 8x 3.14x800 = 20096 (decimeter) =2009.6 (meter);

2

The developed diameter is 5 ∶ 3 = 10 ∶ 6. Enlarged diameter10m; Or expanded diameter =5x6÷3.

Radius =10 ÷ 2 = 5m

Circumference of the bottom = diameter x π ≈10x3.14 = 31.4 (m)

Area = radius x radius xπ≈5x5x3. 14=78.5 (square meter)

three

The circumference of the circular fountain is 62.8m, and the diameter = circumference÷π ≈ 62.83.14 = 20 (m).

Guardrail diameter = circular fountain diameter +3+3=20+3+3=26 (m)

Guardrail length = guardrail diameter x π ≈ 26x3.14 = 81.64 (m)