Fluent adding and subtracting within 1000
Fluently add and subtract within 1000 using strategies and algorithms based on place value, properties of operations, and the relationship between addition and subtraction
What a learner can do afterwards
- Add two three-digit numbers fluently using an efficient method
- Subtract three-digit numbers fluently, including with regrouping
- Choose the most efficient strategy based on the numbers involved
The lesson
Being fluent means you add and subtract three-digit numbers quickly and correctly. You already know how to regroup ones, tens, and hundreds. Now the goal is speed: pick whichever strategy fits the numbers in front of you.
Jamal subtracts 672 − 348 with the written method. Ones: 2 is less than 8, so he regroups a ten: 12 − 8 = 4. Tens: 6 − 4 = 2. Hundreds: 6 − 3 = 3. The answer is 324.
Look at the numbers first. If one is close to a round number like 300 or 500, rounding and adjusting can be faster. If the numbers don't round nicely, the written method with regrouping works every time.
Fluent means fast and correct: round and adjust for friendly numbers, and regroup for the rest.
Watch it
Where it sits
This opens up
Where this leads
Jobs that lean on this skill. Follow one to see everything it is built on.
8 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.