Final answer:
To find the rate of stuffing envelopes since Tiffany arrived, we need to calculate the number of envelopes stuffed per minute. We can use the given information about the total number of envelopes stuffed after certain time intervals to find the rate at which they are being stuffed. Setting the rates at different time intervals equal to each other and solving the equation will give us the initial number of envelopes stuffed, which we can substitute back to find the rate.
Step-by-step explanation:
To find the rate at which envelopes are being stuffed since Tiffany arrived, we need to calculate the number of envelopes stuffed per minute. We can subtract the initial number of envelopes stuffed from the total number of envelopes stuffed after a certain time to find the number of envelopes stuffed in that time period. Then we divide that number by the time in minutes to get the rate. In this case, 40 minutes after Tiffany arrived, they had stuffed a total of 650 envelopes. So, the number of envelopes stuffed in 40 minutes is 650 - x, where x is the initial number of envelopes stuffed. Therefore, the rate is (650 - x) / 40 envelopes per minute.
Similarly, 20 minutes after Tiffany arrived, they had stuffed a total of 400 envelopes. So, the number of envelopes stuffed in 20 minutes is 400 - x. Therefore, the rate is (400 - x) / 20 envelopes per minute.
Since the rate is the same for both time periods, we can set the two rates equal to each other and solve for x: (650 - x) / 40 = (400 - x) / 20. Solving this equation will give us the initial number of envelopes stuffed, x. Once we have x, we can substitute it back into either rate equation to find the rate at which they are stuffing envelopes since Tiffany arrived.