42÷7=6 (double precision);
Answer: On average, 6 pairs are sold every day.
(2) 12> 1 1> 10>6>3;
Number 24 is the most, mode 24.
23,23,23,23.5,23.5,23.5,23.5,23.5,23.5,24,24,24,24,24,24,24,24,24,24,24,24,24,24.5,24.5,24.5,24.5,24.5,24.5,24.5,24.5,24.5,24.5,
24.5,25,25,25,25,25,25,25,25,25.
No.20 and No.21are both 24, and their average value is also 24; So the median of this set of numbers is 24.
(3) The bar chart is as follows: