Use reasoning to answer the following question.
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?

21
An additional three - quarters of 12cm is needed which is 12cm * (3 / 4) = 9cm.

The total length required is 12cm + 9cm = 21cm.

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So, the final answer is 21