You have three blue shirts and one red shirt. How many shirts do you have? Three plus one equals four, three plus one equals five, or three plus two equals four.
Which number sentence matches the picture? So here we have a group of three blue shirts and we have one red shirt. We can write this as three plus one. How many shirts is that altogether? So altogether, we have one, two, three, four shirts. So the number sentence which matches the picture is three plus one equals four.