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Data & spreadsheets · course 35 of 105

Excel Formulas the Office Runs On

Build work spreadsheets that don’t quietly break, from the $ sign and filling down to IF, SUMIFS, XLOOKUP, text and date cleanup, and dynamic arrays.

5 modules

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What it teaches

The formulas office work runs on: the $ sign and filling down (a common source of silently wrong sheets), COUNT vs COUNTA, IF and nested tiers, COUNTIF / SUMIF / SUMIFS, VLOOKUP / XLOOKUP / INDEX-MATCH (and why a missing FALSE gives wrong numbers with no error), and cleaning text and dates (TRIM, LEFT/MID/FIND, EOMONTH, DATEDIF). The AI asks 3 questions, places you, then gives you one task at a time on a small fixed workbook, works out what your formula returns in every cell it fills, and makes you redo what you got wrong.

How long

2-4 short sessions. 72 questions in all (51 exercises, 21 concept questions); optional M4 adds 20 (14 exercises, 6 concept), about one more session. Then a 10-item final test. The tutor gives a one-line save code at the end of each session; paste it into a new chat to carry on.

The modules

5 modules, drilled one item at a time. The ones marked optional are offered along the way.

  1. M0

    Cells, math, ranges and the $ sign

    Write a formula / READ a formula / concept

  2. M1

    IF, AND/OR, IFERROR, COUNTIF and SUMIF

    Write a formula / READ a formula / concept

  3. M2

    VLOOKUP, XLOOKUP, INDEX/MATCH

    Write a formula / READ a formula / concept

  4. M3

    Text and dates

    Write a formula / READ a formula / concept

  5. M4

    Dynamic arrays: FILTER, UNIQUE, SORT, SORTBY and LEToptional

    Write (the answer spills from L2) / READ / concept

Before it teaches, it asks

  1. 1
    What do you need Excel for (job, a new role, an interview test, a class)? Which app: Excel 365 (or Excel on the web), Excel 2024, Excel 2021, Excel 2019, an older Excel, Google Sheets, Numbers, no idea? Can you open a spreadsheet right now? And what trips you up most, if anything?
    AI voice (ElevenLabs)
  2. 2
    Write a formula for L2: total revenue.
  3. 3
    Write a formula for H2 that you can fill down to H13: Yes if Units is 10 or more, otherwise No.

What’s exact, and what isn’t

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Straight from the course’s own notes.

Exact
Every expected value, every “also right” formula and every trap was computed by a formula engine (which follows Excel) on this workbook, 2026-10-08: 194 formulas, filled down cell by cell. M4 (2026-10-09): 41 more, each read across its whole spill. The tutor grades by values, not by matching your text, so any correct formula scores.
Judgment
When your formula isn’t one the key lists, the AI works it out by hand against the workbook. It shows its work on a Check: line and won’t mark you wrong without naming the cell that differs. If you can open the workbook, paste what your app shows and the app wins.
Not in it yet
Pivot tables, charts, conditional formatting, macros, Power Query, tables, LAMBDA, SEQUENCE.