13. At the lumber yard, there were logs 6 m and 8 m long of the same thickness. Which logs are more advantageous to take in order to get more pieces with fewer cuts when cutting them into 1-meter pieces?
13. It is more profitable to take logs from which more pieces can be obtained with fewer or the same number of cuts. From a six-meter log, 6 pieces can be obtained with 5 cuts, while from an eight-meter log, 8 pieces can be obtained with 7 cuts. Let's compare the number of pieces obtained from these logs with the same number of cuts. For the numbers 5 and 7, the least common multiple is 35. Therefore, taking 7 six-meter logs and making 35 cuts, we will get $6 \cdot 7=42$ pieces, while from five eight-meter logs with the same number of cuts, we will get $8 \cdot 5=40$ pieces. Therefore, it is more profitable to take six-meter logs.