A circular reservoir is 25.12 meters when walking around it. What's its floor area? A circumference is 31.4 decimeters. What's the area of this circle

A circular reservoir is 25.12 meters when walking around it. What's its floor area? A circumference is 31.4 decimeters. What's the area of this circle

25.12/3,14=8 3.14*(8/2)²=50.24m²
31.4/3.14=10 3.14*（10/2）²=78.5dm²

The perimeter of a round flower bed is 31.4 meters. How many square meters does it cover?

2, = 3.14 × 52, = 3.14 × 25, = 78.5 square meters. A: this flower bed covers an area of 78.5 square meters

Build a 1cm wide path outside a circular pool with a circumference of 15.7. What's the area of the road?

Inner radius 15.7 △ 3.14 △ 2 = 2.5m
Outer radius 3.5 + 1 = 3.5
Area 3.14 × (3.5 × 3.5-2.5 × 2.5)
=3.14×6
=18.84 square meters

Build a 1 meter wide circular path around a circular pool with a perimeter of 94.2 meters. What's the area of the path?

This is to find the area of the ring, and to find the diameter according to the circumference, d = 94.2 △ 3.14 = 30, s ring = s outer-s inner = 3.14 * (31 & # 178; - 30 & # 178;) = 3.14 * 61 = 191.54