An additional three-quarters of 12cm is needed which is 12cm*(3/4) = <<12*(3/4)=9>>9cm

The total length required is 12cm+9cm = <<12+9=21>>21cm

# Answer

21
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
Roland needs a length of thread to complete an exercise. He has a 12cm long thread but his teacher says he needs an additional three-quarters of what he has. What is the total length required?
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
21
Roland needs a length of thread to complete an exercise. He has a 12cm long thread but his teacher says he needs an additional three-quarters of what he has. What is the total length required?
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