Addition and subtraction problems in words
A story gives some numbers and hides one. How do you tell from the story alone whether to add or subtract to find it?
Where you are 7 inside
What this area is about
A story problem never says “add” or “subtract”. It says that things joined, left, sat side by side or were compared, and it hides one number. The work is reading the shape of the story: which amounts are parts, which is the whole, and which one is missing. Then the operation follows.
How these fit together
First stories. Acting out stories within 10 turns a little joining or taking-away story into objects, a drawing and an equation such as 4 + 3 = 7.
Where the missing number sits. Problems with the start, change or result missing gives the end of the story and hides the change or the start, within 20. Total or result missing gives both numbers and asks how many in all or how many are left. Starting amount missing runs a story backward to its start, with two-digit numbers.
Comparing. How many more and how many fewer covers stories where nothing moves: two amounts are compared, and the story may hide the gap or either amount.
Tools for harder stories. Bar models are a drawing that shows parts and whole for any of these stories. Two-step problems need one answer found before the next.
A path through it
Start by acting stories out within 10, then stories with the change or the start missing. Take total-or-result-missing and start-missing stories next, then comparing stories, then bar models, and finish with two-step problems.
From here, stories that mix all four operations open up in problems using several operations.