A Grade 3 in the CXC CSEC (Caribbean Secondary Education Certificate) typically corresponds to a percentage range of about 70% to 79%. This is based on the grading system where:

• Grade 1 is around 90% and above,
• Grade 2 is around 80% to 89%, and
• Grade 3 is around 70% to 79%.

The lowest acceptable passing grade (Grade 3) is often considered to start from 70%. Anything below 50% would generally be considered a failing grade (Grade 6 or lower) in the CXC system. So, a Grade 3 indicates a good pass in the 70%-79% range for the CXC exams. This aligns with the explanation that the minimum score to earn a Grade 3 is about 70 marks out of 100, as described in the modified grading approach for CSEC subjects.