To find the rate of pounds per week, we need to divide the total amount of aluminum cans collected over the last 4 weeks by the number of weeks:
Rate of pounds per week = Total pounds collected / Number of weeks
In this case, the total pounds collected is 90, and the number of weeks is 4. So, we can plug these values into the formula:
Rate of pounds per week = 90 pounds / 4 weeks
Simplifying this expression, we get:
Rate of pounds per week = 22.5 pounds/week
*Therefore, the deli accumulated aluminum cans at a rate of 22.5 pounds per week over the last 4 weeks.