No wonder US schools are so poorly rated. They get very basic stuff very wrong like this. 2+2=5 is probably in the previous chapter.
2.4 + 2.4 = 4.8, rounded is 5.
Therefore, 2 + 2 = 5.
I was taught this as a "mind teaser" in middle school once. It was supposed to be cute and fun, but just ended up confusing half the class.