Average marks in Mathematics of Section A comprising 30 students is 65 and that of Section B comprising 35 students is 70. What are the average marks (approximately) of both the sections if it was detected later that an entry of 47 marks was wrongly made as 74?

The correct total marks for Section A is 30 multiplied by 65, which equals 1950. The correct total marks for Section B is 35 multiplied by 70, which equals 2450, but correcting the error of 47 entered as 74 means subtracting 27, leaving 2423. The combined correct total is 1950 plus 2423, which equals 4373. Dividing this total by the 65 students gives an overall average of approximately 67.28.

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