When the radius of a circle increases from 6 cm to 9 cm, the area of the circle increases () A. 9 π square centimeter B. 45 square centimeter C. 45 π square centimeter

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• 1. If the radius of a circle increases by 10%, the area of the circle increases by ()%
• 2. When the radius of a circle is three times the original, the area of the circle is () times larger
• 3. The diameter of circle a is 4cm, the radius of circle B is 6cm, and the area ratio of circle a and circle B is () A 4mm precision instrument parts, drawing on the map has 4cm, the scale is () The () and () of a circle are in direct proportion How many times does it take to transport 2700 tons X is proportional to y () 1. X + y = 30 2. Y = 2 / 3 x 3. Xy = 2 / 3
• 4. It is known that the sum of the radii of the two circles is 6cm, the perimeter of the big circle is 25.12cm, the area of the small circle is () and there are two big and small circles, the radius of the big circle is 6cm, and the diameter of the small circle is 4cm The difference between the area of these two circles is very urgent
• 5. When the radius of a circle increases from 4cm to 6cm, how many square centimeters does the area of the circle increase?
• 6. 1. Known: radius of circle r = 2cm, calculate area of circle 2. Known: diameter of circle d = 6cm, calculate area of circle 3. Known: the circumference of the circle is 6.28cm, find the area of the circle 4. It is known that the arc length of 30 ° center angle is 1.57cm, and the area of the arc is calculated The radius of the big turntable in the amusement park is about 50 meters. How many square meters is the area of the circular surface produced by its rotation? How long is the route for tourists to take this big turntable to rotate for a week? The first question is to ask () and the second question is to ask ()
• 7. The radius of a circle is π M. what is the area of the circle
• 8. In a square with a circumference of 12 cm, draw a circle with the side length of the square as the diameter. How many cm is the circumference of the circle? Is that 9.42 cm?
• 9. A square with a side length of 16 cm, draw a circle, how many cm is the radius of the circle (), how many cm is the circumference of the circle ()
• 10. The perimeter of a square is equal to that of a circle. If the side length of a square is known to be 3.14 cm, then the radius of the circle is
• 11. The radius of the circle is doubled and its circumference is doubled______ It expanded to its original size______ ．
• 12. The radius of a circle is 4cm. What are the perimeter and area of the circle?
• 13. For two circles with radius of 4cm and 6cm respectively, the perimeter ratio of small circle and large circle is (), and the area ratio is ()
• 14. The radius of a circle is 6cm, and the circumference of the semicircle is () times?
• 15. The radius of a circle is 2. What's the circumference and area of the circle? One more question The mass ratio of chocolate to milk is 2:9 {1} If you have 400 grams of chocolate, how many grams do you need
• 16. The radius of the circle has increased from 4 decimeters to 6 centimeters, and the area of the circle has increased by () square centimeters a, 6b, 20c, 20c
• 17. If the radius of a circle is a centimeter and 2: a = A: 3, the area of the circle is () square centimeter A2 / 3 * 3.14 B6 * 3.14 C cannot be calculated
• 18. If the radius of a circle is a centimeter and 2: a = A: 3, the area of the circle is () square centimeter A. 23 π B. 6 π C. 6D
• 19. A circular ring, the diameter of the outer circle is 5cm, the radius of the inner circle is 3cm, how many square meters is its area?
• 20. The radius of the outer circle of a ring is 5cm longer than that of the inner circle, and the radius of the inner circle is 3cm. What is the area of the ring?