Final answer:
There were 110 robberies in Springfield in 2011.
Step-by-step explanation:
To find the number of robberies in Springfield in 2011, we can use the given information that robberies were up 40% to 154 in 2012 from 2011. Let's assume the number of robberies in 2011 is x.
Since the robberies increased by 40% from 2011 to 2012, we can calculate the 40% increase as 0.4x. Adding this increase to the number of robberies in 2011, we get x + 0.4x = 154. Solving this equation, we find that 1.4x = 154, and dividing both sides by 1.4, we get x = 110. Therefore, there were 110 robberies in Springfield in 2011.