Answer:
1. 2.19 cm
2. 30.2m
3. 2.65 cm
4. 9.33cm
5. 14.2 mm
6.497000km²
Step-by-step explanation:
Use the pi button on a calculator and give answers to 3's.f.
1. A circle has an area of 15 cm². Find its radius.
Area of a circle = πr²
15cm² = π × r²
r² = 15cm²/π
r² = 4.7746482927568605
r = √(4.7746482927568605)
r = 2.1850968612 cm
Approximately to 3 s.f ≈ 2.19 cm
2. A circle has a circumference of 190 m. Find its radius.
The circumference of a circle = 2πr
C = 190m
Hence:
190m = 2πr
r = 190m/2π
r = 30.239439187m
Approximately to 3 s.f = 30.2m
3. Find the radius of a circle of area 22 km².
Area of a circle = πr²
22km² = π × r²
r² = 22km²/π
r² = 7.002817496
r = √(7.002817496)
r = 2.6462837142 cm
Approximately to 3 s.f ≈ 2.65 cm
4. Find the radius of a circle of circumference 58.6 cm.
The circumference of a circle = 2πr
C = 58.6cm
Hence:
58.6cm = 2πr
r = 58.6cm/2π
r = 9.3264796652cm
Approximately to 3 s.f = 9.33cm
5. A circle has an area of 16 mm². Find its circumference.
Step 1
Find the radius
Area of a circle = πr²
16 mm² = π × r²
r² = 16 mm²/π
r² = 5.092958178940651
r = √(5.092958178940651)
r = 2.2567583342mm
Circumference of a circle = 2πr
Circumference = 2 × π × 2.2567583342
= 14.179630807mm
Approximately to 3 s.f ≈ 14.2 mm
6. A circle has a circumference of 2500 km. Find its area.
Step 1
Find the radius
The circumference of a circle = 2πr
C = 2500km
Hence:
2500km = 2πr
r = 2500km/2π
r = 397.88735773km
Area of a circle = πr²
Area of the circle = π ×(397.88735773km)²
Area of the circle = 497359.19716km²
Approximately to 3 s.f = 497000km²
