Goal: reach 120 by trading at 119 + 1 and show 120 as a hundred plus two tens or twelve tens. Prepare: hundred square, two strips, ten singles, twelve verified strips, Day 27 cards.
- Notice, 3: Build 118 as hundred + ten + eight. Ask for one more and what the next added one will require.
- Model, 5: Add one to 119. Trade ten loose ones for another ten-strip. Display 100 + 20 = 120 and 12 tens = 120. Audit twelve strips in ten-and-two groups; do not count a bundle as an extra amount when its strips are still displayed beside it.
- Guided, 8: Cards A/B represent 117 and 119. Move 117→118→119→120 on a chart and model; ask which change creates a new ten and which quantity remains the same during that trade.
- Independent, 6: Card C gives 120. Learner chooses hundred + two tens or twelve strips, explains their equivalence, and names one less than 120. Two modes are offered; writing 120 is not the only acceptable response.
- Exit, 3: Show one hundred, one ten and ten singles. Ask for total and exchanged form. Key: 120 and one hundred + two tens + zero singles. If 1110 appears, exchange the ten singles and reread all columns.