Hi Kaeruno,
The radius of the stool is 21 cm. To find the circumference, multiply this by 2 pi, since multiplying by 2 gives you the diameter and multiplying that by pi give the circumference.
2pi * 21cm
= pi * 2 * 21cm
= pi * 42cm
= (22/7) * 42cm
= 924/7 cm
= 132 cm.
The circumference is 132 cm.
If you have any further questions, feel free to message me!
Sincerely, taeuknam.
