Step 1: Converting the given statement into a mathematical equation
Total meters of ribbon =412+616+329
=4×3+13+6×6+16+3×9+29
=12+13+36+16+27+29
=123+376+299
Step 2: Simplifying the obtained expression to find the total quantity that he bought
=123+376+299
=13×6+37×3+29×218
[LCM of (3,6,9) =18]
=78+111+5818
=24718m
Hence, he bought 24718 or 131318m of the ribbon.