Final answer:
The constant of proportionality relating cost to pounds of grapes is calculated by dividing the cost by the number of pounds; for 3 pounds of grapes costing $6.75, it is $6.75 divided by 3, resulting in $2.25 per pound.
Step-by-step explanation:
The constant of proportionality that relates the cost in dollars (Y) to the number of pounds of grapes (X) is calculated by dividing the total cost by the number of pounds.
Given that the cost of 3 pounds of grapes is $6.75, we divide $6.75 by 3 pounds to find the constant of proportionality.
Constant of proportionality = Total Cost / Number of Pounds
Constant of proportionality = $6.75 / 3 pounds
Constant of proportionality = $2.25 per pound
Thus, the constant of proportionality is $2.25 per pound, which means for every pound of grapes, the cost increases by $2.25.