OG详解-OG7 数学2 Q13

The correct answer is 4.41. The area, A, of a circle is given by the formula A = πr² ,  where r is the radius of the circle. It’s given that the area of the circle is bπ square inches, where b is a constant, and the radius of the circle is 2.1 inches. Substituting bπ for A and 2.1 for r in the formula A = πr²  yields bπ = π (2.1²). Dividing both sides of this equation by π yields b = 4.41. Therefore, the value of b is 4.41.