The first math problem is to find out how many square centimeters the area of a big circle is larger than that of a small circle. ? How many square centimeters is the area of this circle?
Solution: (1) What is the square of the radius of the small circle? 50÷π=50/π cm2 (2) What is the square of the radius of the great circle? 50/π× (1+20% )× (1+20%) = 72/π cm2 (3) What is the area of the great circle in square centimeters? π × 72/π =72 cm2 (4) How many square centimeters is the area of the great circle larger than that of the small circle? 72-50=22 cm2 A: The area of the big circle is 22 cm2 larger than that of the small circle.