Lesson 2.1 · Word Problems
Add-to and take-from problems
A word problem is a little story with a math question inside. In some stories, things join a group. In others, things leave a group. Your job is to figure out which one is happening.
Add to: the group gets bigger
In an add-to story, more things come. The group grows, so you add.
"Mia has 6 shells. She finds 3 more." The group gets bigger: .
Take from: the group gets smaller
In a take-from story, some things go away. They are eaten, given away, or they fly off. The group shrinks, so you subtract.
"There are 9 birds. 4 fly away." The group gets smaller: .
Ask: bigger or smaller?
Things join the group, so it gets bigger: add.
Things leave the group, so it gets smaller: subtract.
Solve it in steps
- Read the story. Picture it.
- Ask: did the group get bigger or smaller?
- Write a number sentence and solve it.
- Check that your answer makes sense.
Worked example: Frogs on a log
5 frogs sit on a log. 4 more frogs hop on. How many frogs are on the log now?
🐸 🐸 🐸 🐸 🐸 ➕ 🐸 🐸 🐸 🐸
More frogs came, so the group got bigger. Add: . There are 9 frogs.
Worked example: Eating grapes
Leo has 12 grapes. He eats 5. How many grapes are left?
Some grapes are gone, so the group got smaller. Subtract: . There are 7 grapes left.
Worked example: A missing part
Ana has 8 stickers. Her friend gives her some more. Now she has 11. How many stickers did her friend give her?
This time we know the start (8) and the end (11). We need the part that was added:
Count on from 8: nine, ten, eleven. That is 3 counts. Her friend gave her 3 stickers. Check: . ✓
Common mistake
Don't just add every number you see! In the sticker story, 11 is the total at the end. Adding would be wrong. Always ask what each number means.
Tip
Check your answer. If things joined, the answer should be more than the start. If things left, it should be less.
Practice
There are 7 kids on the slide. 3 more kids come. How many kids are there now?
Type a number.
Sam has 9 balloons. 5 balloons pop. How many balloons does Sam have now?
Type a number.
There are 14 apples in a bowl. Dad takes 6 apples. Which number sentence tells how many apples are left?
A bus has 8 people on it. At the next stop, 7 more people get on. How many people are on the bus now?
Type a number.
Kim had 16 crayons. She gave 7 to her brother. How many crayons does Kim have left?
Type a number.
There are 6 ducks in a pond. Some more ducks swim over. Now there are 11 ducks. How many ducks swam over?
Type a number.
Raj had 13 marbles. He lost some. Now he has 9. How many marbles did he lose?
Type a number.