24 cm + 18 cm
Maria has a blue ribbon that is twenty-four centimeters long. She has a red ribbon that is eighteen centimeters long.
If she lays them end to end, how long are the two ribbons together?
We can write that as twenty-four plus eighteen equals something.
Let's use a number line from zero to fifty to add the lengths.
We start at twenty-four — the length of the blue ribbon.
Now we add eighteen. First we hop ten. Twenty-four plus ten is thirty-four.
Then we hop eight more. Thirty-four plus eight is forty-two.
So twenty-four plus eighteen equals forty-two.
The two ribbons together are forty-two centimeters long. Nice work!