Which formula uses pi approximated as 3.14 to calculate circle area with radius r?

Which formula uses pi approximated as 3.14 to calculate circle area with radius r?

• A. (3.14 x r)^2 = A
• B. 3.14 x r^2 = A
• C. 2 x 3.14 x r = A
• D. 3.14 x d^2 = A

Answer: (B)

Area of a circle is π times the radius squared. Using π ≈ 3.14, the area becomes A ≈ 3.14 × r^2. That matches the form 3.14 × r^2 = A, since it directly applies the area formula with the approximate π. The other expressions describe something else or misplace the squared term: squaring (3.14 × r) would give (πr)^2, which isn’t the correct area formula; 2 × 3.14 × r is the circumference, not the area; and 3.14 × d^2 uses diameter squared in a way that isn’t correct for circle area (in terms of diameter, A = (π/4) d^2). For example, with r = 5, the area is about 78.5 square units.

Area of a circle is π times the radius squared. Using π ≈ 3.14, the area becomes A ≈ 3.14 × r^2. That matches the form 3.14 × r^2 = A, since it directly applies the area formula with the approximate π. The other expressions describe something else or misplace the squared term: squaring (3.14 × r) would give (πr)^2, which isn’t the correct area formula; 2 × 3.14 × r is the circumference, not the area; and 3.14 × d^2 uses diameter squared in a way that isn’t correct for circle area (in terms of diameter, A = (π/4) d^2). For example, with r = 5, the area is about 78.5 square units.