The three-card activity connects 305, 350, 503 with hundreds, tens, ones, and the changing values of digits five and three. Checks distinguish a blank answer from a legitimate zero and count each completed card only once.
Use the worked example
Choose 305 and enter 3 hundreds, 0 tens, and 5 ones. Enter Ones and 5 for digit five, then Hundreds and 300 for digit three. Select Check seven answers. Compare the result with 350 and 503, filling the fields again after each change.
Explain the evidence for the answer
Do not accept “five” as a complete answer to both the position and value questions. “Tens” names a position; “50” names the value of five in that position. For PV2, five tens contribute 5 × 10 = 50, while the zero ones contribute zero.
Comparing PV1 and PV2 is also useful: three stays in the hundreds place with value 300 even while the other two digits exchange positions. Comparing PV1 and PV3 shows that three can instead have value three in the ones place.
The model uses labeled symbols: a hundreds symbol contributes 100, a tens symbol contributes 10, and a ones symbol contributes 1. Its text states both the group count and contribution. Read those labels together; the symbol's printed size does not represent a physical measurement.
For 305, the model shows three hundreds symbols and five ones symbols. Tens still has its own heading, count zero, and contribution zero. Ask the learner to point to that column before writing the numeral, so an absent group does not become an omitted position.
Deleting the zero from the written numeral gives 35 = 30 + 5, not 305 = 300 + 0 + 5. The zero is a positional placeholder; it is not an unanswered worksheet cell.
After checking, ask the learner to finish this on paper: “There are ___ hundreds, ___ tens, and ___ ones. Removing the zero changes ___ to ___.” The page compares the seven entries, while the teacher discusses the explanation. A correct match does not reveal how the learner reasoned.
2 × 100 + 10 × 10 + 5 × 1 = 200 + 100 + 5 = 305
Bundle the ten tens into one hundred. The model becomes three hundreds, zero tens, and five ones, still totaling 305. No quantity has been added or removed.
Ten tens is a valid amount of base-ten units in that model. It is not a single digit to enter in the tens column of the standard numeral 305. Explain that distinction before calling a response wrong: the digital canonical-count task asks for digits zero through nine, while the regrouping task allows a noncanonical bundle count.
Check requires a selected card and all seven known responses before comparing with the key. A blank is incomplete, but zero is a supplied answer. Feedback identifies the specific count, position, or value that needs review. Editing a response clears the old feedback until Check runs again.
Copy a prompt for this example
Create one HTML place-value practice page for the numbers 305, 350, and 503. Put three number buttons above a simple hundreds, tens, and ones model. Keep the tens heading visible when its count is zero. Use labeled symbols and text counts rather than relying on pictures alone.
Provide seven answer fields: hundreds count, tens count, ones count, position of digit five, value of five, position of digit three, and value of three. Start on 305 with every answer blank. Accept position names without regard to capitalization.
For 305 the answers are 3, 0, 5, Ones, 5, Hundreds, 300. For 350 they are 3, 5, 0, Tens, 50, Hundreds, 300. For 503 they are 5, 0, 3, Hundreds, 500, Ones, 3. Check must distinguish an unanswered field from a legitimate zero and identify which answers need review.
After a complete correct response, show the expanded form. Track each number checked correctly at least once, up to three; repeated checks cannot add another completion. Changing a number blanks the current answers, while editing an answer clears current feedback.
Include the extension that two hundreds, ten tens, and five ones equal 305, without accepting ten as a canonical tens digit. Reset clears prior completions and returns to blank 305 answers. Use large readable type and stacked controls on phones. Return the complete HTML page.
Choose the card comparison your class needs and ask students to explain the zero in writing. Preview the prepared HTML activity in NOS while checking the counts and expanded forms. Keep that written explanation for teacher review; a successful seven-field match is local practice feedback.