Number and Operations in Base Ten
This domain tests place value through the thousands and flexible adding and subtracting within 1,000. You need to read and write numbers in standard, expanded, and word form, round to the nearest 10 or 100, and add or subtract with regrouping.
Core rules
- Each place is ten times the place to its right: in 3,472 the 4 means 400.
- Expanded form: 3,472 = 3,000 + 400 + 70 + 2.
- Rounding: find the target place, then look at the digit to its right. A 5 or more rounds up.
- Add and subtract by place, regrouping when a column reaches 10 or more, or when you must borrow.
Worked example
Add 452 + 379. Ones: 2 + 9 = 11, write 1 and carry 1 ten. Tens: 5 + 7 + 1 = 13 tens, write 3 and carry 1 hundred. Hundreds: 4 + 3 + 1 = 8. Answer: 831. Estimate check: 450 + 380 = 830, so 831 is reasonable.
Traps that cost marks
- Lining up digits by their left edge instead of by place value, so tens land under hundreds.
- Forgetting the carried ten or hundred after regrouping.
- Rounding 650 to the nearest hundred as 600; the 5 in the tens place rounds the hundreds digit up to 700.
- Writing 4 hundreds as 4 when the answer needs 400.