1. The problem asks for the total length of the line of shoes for students whose shoe lengths are less than 21 centimeters. 2. From the data, shoe lengths less than 21 cm are 20 cm and 20 1/2 cm. 3. Count the number of shoes at each length: - At 20 cm: 1 shoe - At 20 1/2 cm: 4 shoes 4. Calculate the total length contributed by each group: - For 20 cm shoes: $1 \times 20 = 20$ cm - For 20 1/2 cm shoes: $4 \times 20.5 = 82$ cm 5. Add these lengths to find the total length of the line: $$20 + 82 = 102$$ 6. Therefore, the line of shoes for students with shoe lengths less than 21 cm is 102 centimeters long.