Answer:
The student made a mistake in step 4
The length of the radius should be 6 cm
Step-by-step explanation:
Let us write each step to find the radius of a circle from its circumference
Step 1:
∵ C = 2πr
∵ C = 12π
Step 2:
Equate 12π by 2πr
∴ 12π = 2πr
Step 3:
Divide both sides by 2π
∵ 
Step 4:
∴ 6 = r
∴ The radius of the circle is 6 cm
The student mad a mistake he divided the left hand side by 2π and the right hand side by 2 only he left π with r
Step 4:
∴ 6 = πr
So he divided both sides again by π
Step 5:
∵ 
Step 7:
∴
= r
The student made a mistake in step 4
The length of the radius should be 6 cm