1 - Introduction ~5 mins
Welcome
Your Something Real budget only helps if the numbers are trustworthy. Today you spot red error codes, fix the formulas behind them, and run a calm sanity check before anything goes into a Key Assignment sheet.
By the end of this lesson, you will be able to:
- Recognise #DIV/0!, #VALUE!, #REF! and #NAME?
- Trace and fix broken cells with a sanity-check habit
- Check totals against real project numbers
- Log what you checked on {{code:05_project_budget}}
Missing file? Tell your teacher and open the starter template from Project Portfolio > {{code:05_budget}}. Rename it {{code:05_project_budget}} before Error Lab.
Warm-up
Quick call-out: a till total once came out absurd (€400 for coffee, or a €0.02 split bill). What would you check first — the numbers typed, or the calculation?
2 - Key Concepts ~5 mins
Error codes mean "I cannot finish this calculation." Learn the four you will meet most often. After the lab you will also use a sanity check: does this result make sense for real costs?
| Concept | Why it matters | Example |
|---|---|---|
| #DIV/0! — divided by zero or blank | A zero quantity or blank denominator breaks averages and cost-per-unit maths | Cost per unit {{code:=B2/C2}} when cups ordered is 0 on a Work Experience stock sheet |
| #VALUE! — text where a number was needed | One mistyped word in a number column can break a whole total row | {{code:=B3*C3}} fails if Quantity holds the word "three" instead of {{code:3}} |
| #REF! — points at a cell that no longer exists | Deleting a column or row can shatter formulas that still look fine at a glance | You delete a Quantity column that line totals still referenced; those totals flip to #REF! |
| #NAME? — function name typed wrong | A single extra letter stops the calculation completely | Typing {{code:=SUMM(D2:D5)}} instead of {{code:=SUM(D2:D5)}} |
Worked snapshot: Error Lab
- Build a short {{code:Error_Lab}} tab and set up three common errors on purpose, then fix each one.
- Pattern every time: click the red cell → read the formula bar → fix the data or the spelling → Enter → check the number looks human.
- Your teacher shows #REF! after a deleted column and how Undo brings the sheet back.
3 - Step-by-step Task ~18 mins
Open {{code:05_project_budget}} from Project Portfolio > {{code:05_budget}}, add a practice sheet tab called {{code:Error_Lab}}, set up three common errors on purpose (#DIV/0!, #VALUE!, #NAME?), and fix each one using the formula bar. #REF! is watch-only on the board (optional quick try if you want). Line totals stay as cost × quantity so the lab matches a real budget. The win is the repair pattern — click, formula bar, fix, Enter — not every optional polish. If your teacher gives you a starter {{code:Error_Lab}} sheet, start at the first formula step.
4 - Common Issues ~7 mins
Common Issues
| Issue | Solution |
|---|---|
| I still see #DIV/0! after I typed a number in the quantity cell | Check you edited the cell the formula actually divides by. Click the red cell, read every cell reference in the formula bar, and confirm none of those cells are blank or zero. |
| I fixed the spelling but #NAME? will not clear | Look for a missing {{code:=}} at the start, a space inside the name ({{code:SU MM}}), or an extra letter ({{code:SUMM}}). Clear the cell and re-type {{formula:=SUM(D2:D5)}} cleanly. |
| Undo did not bring my deleted column back | Re-insert the column, re-enter the values, then rewrite each broken formula by clicking the cells again so references rebuild correctly. |
| No red errors, but my total looks impossibly large or tiny | That is a sanity-check fail, not an error code. Click the total, check the range in the formula bar, and compare against a rough estimate of your real project costs. |
Teacher model: audit a live budget
Watch your teacher on a sample budget (not your file yet):
- Click one total or average cell and read the formula bar out loud.
- Compare the result to a rough estimate ("four items around €25 each should be near €100, not €1,000").
- Pick the biggest cost cell, change it by €1, confirm the total moves, then put the real figure back.
- If something is off, fix the data or the range, then type one line in a Sanity-check log.
Start your log two rows below your last budget data row (if your last number is in row 18, begin at row 20). Leave this model log on screen while you work:
| Date | Cell/range | Issue | Fix |
|---|---|---|---|
| 12 Mar | C12 | #DIV/0! — quantity was 0 | Set quantity in C12 to 2 |
| 12 Mar | D2:D14 | Total looked about 10× too high | Corrected SUM range so it no longer included a notes cell |
| 12 Mar | — | none further | Line totals match rough estimate for the project |
Type the heading Sanity-check log, then the four column headings, then one row per issue (or a single "none" row if the sheet was already clean).
5 - Independent Practice ~15 mins
Independent Practice
- Open the main budget sheet of {{code:05_project_budget}} (not Error Lab). If the file is missing, tell your teacher and use the starter from Project Portfolio > {{code:05_budget}}, renamed {{code:05_project_budget}}.
- Scan every formula cell and clear any red error codes (#DIV/0!, #VALUE!, #REF!, #NAME?).
- Sanity-check: pick your biggest cost cell, change it by €1, confirm the total moves, put the real figure back. With a partner, say one rough estimate out loud for your project totals.
- Two rows under the last data row, add a Sanity-check log with Date | Cell/range | Issue | Fix (today's date; one row per issue or one "none" row). Keep the same filename — this file in {{code:05_budget}} is your PAT / Key Assignment artefact.
- {{code:05_project_budget}} shows no red error codes (#DIV/0!, #VALUE!, #REF!, #NAME?) in formula cells
- You changed one cost by €1, watched the total update, restored the real figure, and totals still look realistic for your Something Real project
- A Sanity-check log sits two rows under the data with Date | Cell/range | Issue | Fix filled in (or a clear "none" row)
- The same file remains in Project Portfolio > {{code:05_budget}} ready for Practical Achievement Task / Key Assignment evidence
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