Every person is different, but on average you need about 40 hours to 80 hours for each ARE division. Set a realistic study schedule and stick with it. Make sure you allow time for personal and recreational commitments. If you are working full time, my suggestion is that you allow no less than 2 weeks but NOT more than 2 months to prepare for each ARE division. Do NOT drag out the exam prep process too long and risk losing your momentum.
Quoted from page 20 of "Building Systems (BS) ARE Mock Exam (Architect Registration Exam)"
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