Section 5.3 Part 2: Circumference and Area of Circles
A circle has radius 9/5cm. Use π≈22/7to approximate its circumference and area. Enter the answers as reduced fractions.
Correct answers To find the circumference when r=9/5, write the formula for circumference. C=2πr Substitute 22/7 for π and 9/5 for r, then simplify to find C≈2(22/7)(9/5) C≈396/35cm. Now, to find the area when r=9/5, write the formula for area. A=πr^2 Substitute 22/7 for π and 9/5 for r, then simplify to find A≈(22/7)(9/5)^2 A≈1782/175cm^2.
A circle has radius 4in. Use π≈22/7to approximate its circumference and area. Enter the answers as reduced fractions.
To find the circumference when r=4, write the formula for circumference. C=2πr Substitute 227 for π and 4 for r, then simplify to find CC≈2(227)(4)≈1767cm. Now, to find the area when r=4, write the formula for area. A=πr2 Substitute 227 for π and 4 for r, then simplify to find AA≈(227)(4)2≈3527cm2.
A circle has radius 58.7cm. Use π≈3.14 to approximate its circumference and area. Round to one decimal place.
To find the circumference when r=58.7, write the formula for circumference. C=2πr Substitute 3.14 for π and 58.7 for r, then simplify to findCC≈2(3.14)(58.7)≈368.6cm. Now, to find the area when r=58.7, write the formula for area.A=πr^2 Substitute 3.14 for π and 58.7 for r, then simplify to find A≈(3.14)(58.7)^2 A≈10819.5cm2. Answer C=368.6cm A≈10819.5cm2.
