Final answer:
The constant of proportionality between 13 and 16 1/4 is found by dividing 13 by 16.25, which equals approximately 0.8, making option a) 13/16.25 the correct answer.
Step-by-step explanation:
The student is asking to find the constant of proportionality between two numbers, 13 and 16 1/4. To find this constant, you must divide one number by the other. When you divide 13 by 16.25 (which is the decimal equivalent of 16 1/4), you get approximately 0.8, making option a) 13/16.25 the correct answer. However, if you divide 16.25 by 13, you get approximately 1.25, which is not given as an option. Hence, the constant of proportionality in this case is 13/16.25.