C = 2πr = 2 * 3. 14 * 3 = 18.84cm C =πd = 3. 14 * 6 = 18.84cm C = 2πr = 2 * 3. 14 * 5 = 3 1.4cm

3. Xiaodong has a bike ... How many minutes does it take?

66 cm = 0.66 m2000 ÷ (3.14 * 0.66 * 100) = 9.65 minutes = 10 minutes A: It takes about10 minutes.

4. How many centimeters is the minute hand of the non-stop wall clock? What about 45 minutes?

30 minutes = 1/2 45 minutes = 3/42 * 3.14 * 20 *1/2 = 62.8cm2 * 3.14 * 20 * 3/4 = 94.2cma. ..