Codes: AC9M3N01. Target: distinguish 20 040, 20 400 and 2 040. Set out: five-place mat and three printed cards.
- Notice · 2 min. Show the cards side by side. Say: “They share digits but do not show the same quantity. Find the first place where they differ.”
- Think aloud · 6 min. Put
20 040into five columns: 2 ten-thousands, 0 thousands, 0 hundreds, 4 tens, 0 ones. Read “twenty thousand and forty.” Put2 040beneath it, right-aligned; point to its missing ten-thousands place. Compare20 400by the hundreds place. - Guided rename · 5 min. Model
20 040 = 20 000 + 40and20 400 = 20 000 + 400. Ask: “Which zero moved when the four moved?” Avoid saying a zero has no value; here its position communicates an empty place. - Card sort · 7 min. Pairs match spoken descriptions to all three cards, then rebuild from a blank five-place board. Teacher reads “two thousands and four tens”; the learner selects 2 040. Ask for a reason before showing the key.
- Look for an error · 3 min. Show a fictional note
20 040 = 2 040. Invite a correction using place names, not “wrong because it looks longer.” - Brief check · 2 min. Everyone represents 30 506 in five columns. Focus learners identify the thousands and tens as empty. If they say 3 056, rebuild the two numbers with cards.
Access: five tactile compartments with labels and an “empty” token; spoken numeral and print together; learner can direct placement instead of reaching across a desk.