At 1 P.M., there were 16 seagulls on the beach. At 3 P.M., there were 40 seagulls. What is the constant rate of change?
From 1 PM to 3 PM there are 2 hours in between
The number of seagulls has increased by 40 - 16 = 24 during the two hours.
The number of increase PER hour is 24 ÷ 2 = 12 seagulls per hour