N20 · Full next teaching
Previous target
V05D
Target
Keep a one-off cost separate and check a budget
Flexible time
About 8–12 minutes, or shorter visits; unpiloted suggestion.
Prepare
Use scrap paper, group labels and appropriate large counters, or dictate a complete model to a scribe. Work at a table; no purchase, household data or public performance. Keep teacher worked material separate from blank learner spaces.
Complete new neutral task
8 pretend craft kits cost a made-up $10 each plus one $9 fee. The supplied budget is $100. Find the exact cost and amount left or over. All prices are fictional.
Specific criterion
Model repeated cost plus one fixed fee, calculate the exact total and interpret the amount left or over.
Whole teaching sequence
Read the new brief and ask which quantity is missing. Name units before any calculation. Make a card for each purchased kit and one separate fee card. Join the kit-cost total and the fee once. Put the supplied budget on a third card and compare before subtracting.
Build the supplied new example together. Teacher explanation: 8 × $10 + $9 = $89; $100 − $89 = $11 left. Fee paid once. Ask the learner to point to the part of the model that supports each quantity. A fee charged once is not a fee on each item. The count of items is not a dollar amount.
Remove the worked example. Give this changed task privately: Only the one-off fee increases by $2 to $11. Same kits and budget. What changes and what stays? Offer a different response mode if needed without silently changing the mathematical criterion.
Supplied joint model
8 × $10 + $9 = $89; $100 − $89 = $11 left. Fee paid once.
Equivalent offers
Make/draw using original blank group frames.
Explain/sign/point or dictate reasoning.
Type a private note or use paper; a device is optional.
Private changed task after removing model
Only the one-off fee increases by $2 to $11. Same kits and budget. What changes and what stays?
Staff changed-task possibility
Total $91; $9 left. Kit count and repeated cost stay the same.
Observe and decide next teaching
Check the changed response against the named criterion, not against speed, spelling or a preferred-looking diagram. Record the exact support given. If the meaning is still unclear, revisit one group or one constraint with a smaller supplied number, record the change and return later to the original demand.