What is this skill?
Three-digit place value is the idea that the position of a digit tells you what it is worth. In 358, the 3 means 3 hundreds, the 5 means 5 tens, and the 8 means 8 ones, so 358 is 300 + 50 + 8. Second graders build this with base-ten blocks: small cubes for ones, rods of ten cubes for tens, and flat squares of a hundred cubes for hundreds.
Children practice in both directions. They read a picture of blocks and write the number, they name the digit in a given place, and they say what a digit is worth. The 5 in 358 is in the tens place, so it is worth 50, not 5. A big step in second grade is understanding that 100 is a bundle of ten tens, just as a ten is a bundle of ten ones.
Why it matters
Everything in second and third grade arithmetic depends on this. Adding and subtracting three-digit numbers, comparing numbers, rounding to the nearest hundred and skip counting by 100s all assume a child knows what each digit is worth. Regrouping, in particular, only makes sense if a hundred can be traded for ten tens.
Place value is also the doorway to bigger numbers and, later, decimals. The pattern of each place being worth ten times the place to its right keeps going to thousands and millions, and to tenths and hundredths in the other direction. A child who understands it at three digits has the pattern they need.
Common mistakes
- Confusing the digit with its value: saying the 5 in 358 is worth 5. Ask "5 what? 5 ones or 5 tens?" to bring the place back into the answer.
- Writing numbers the way they sound, so "three hundred fifty-eight" becomes 30058. Building the number with blocks or place-value cards that slide on top of each other (300, 50, 8) shows why it has only three digits.
- Losing track of zero. In 407 there are no tens, and children may write 47 or read it as forty-seven. Explain that the zero holds the tens place open so the 4 stays in the hundreds.
- Mixing up the order of the places, especially naming the tens digit when asked for the ones. Labeling columns H, T and O above the number helps until it becomes automatic.
How to help at home
- Make your own base-ten set with dry pasta or beans: loose pieces are ones, small bags of ten are tens, and a bag holding ten bags is a hundred. Build a number and have your child write it.
- Play "What is it worth?" with house numbers, page numbers and prices: "In 362, what is the 6 worth?"
- Use money: a dollar bill, dimes and pennies show hundreds, tens and ones of cents. Three dollars, five dimes and eight pennies make 358 cents.
- Write a number and ask your child to make it 10 more, 10 less, 100 more and 100 less. Watching which digit changes is a quick check of understanding.
Worked examples
These are real questions from the Tutorsaurus hundreds, tens and ones practice, with the answers worked out.
Example 1
In 710, what is the value of the digit 7?
Choices: 699, 703, 700, 698
Answer: 700. The digit 7 is in the hundreds place, so it is worth 700.
Example 2
7 hundreds, 4 tens, 5 ones is…
Choices: 744, 743, 748, 745
Answer: 745. 700 + 40 + 5 = 745.
Example 3
What digit is in the ones place in 882?
Answer: 2. In 882: 8 is hundreds, 8 is tens, 2 is ones.