How your formula is checked
When you press Enter, the formula engine runs your formula on the lesson's sheet. It compares the result with the answer. The feedback appears at once, and it says what went wrong.
The formula engine is our own code. It is not an AI. It follows written rules, and every rule is tested.
What happens when you press Enter
Seven checks, in this order. The first one that fails decides the feedback. Some steps ask you to select cells. There, the click is the answer, and it is checked at once.
-
Is it a formula?
A formula starts with =. If you typed the answer as a number, or forgot the =, the feedback says which.
-
Can it be read?
The brackets and commas are checked, and so is the number of arguments. A missing bracket stops here.
-
Is every function real?
A function name the sheet does not have is named. When a close name exists, it is suggested.
-
Is the answer right?
The formula engine runs your formula on the same sheet and looks at the answer cell. A formula that fills several cells is checked in every cell.
-
Is it built the way the step asks?
If the step teaches SUM, the answer must use SUM. Adding the cells one by one gives the same number, but it is not what the step practises.
-
Does it use the cells?
A formula that works the number out without any cell is not accepted. The answer has to change when the data changes.
-
Checked again when it is saved
Your browser checks at once, so the feedback is instant. When an answer is saved to your account, our server checks it again with the same code.
What the feedback says
From the first step of the SUM lesson, which asks for the total of B2:B6 in B7. The right answer is 36.5.
| You type | You read |
|---|---|
36.5
|
You typed the number. Type a formula that points at the cell, so it stays right when the data changes. |
B2+B3
|
A formula starts with an equals sign. Put = in front of what you typed. |
=SUM(B2:B6
|
Excel cannot read that. Check the brackets and the commas. |
=SUMM(B2:B6)
|
This sheet has no function called SUMM. Did you mean SUM? |
=B2+B3+B4+B5+B6
|
Right number, but not the way this step asks. Use the function in the task. |
=SUM(7.5,9,6.25,8,5.75)
|
This works the number out without using any cell. Point at the cells, so the answer changes when the data does. |
A different formula can still be right
The check compares results, not text. Capital letters and spaces do not matter. On the same SUM step, all of these are marked correct:
=SUM(B2:B6)=sum(b2:b6)=SUM(B2,B3,B4,B5,B6)=SUM(B6,B5,B4,B3,B2)
A step can still ask for the function it teaches. And the formula must read the cells.
What it does not do
- It does not mark you while you type. It marks you when you press Enter.
- It does not give part marks. An answer is right or not yet right.
- It does not score speed. Taking your time costs nothing.
- It does not guess. The helper beside the sheet tries a fix first, where it can. It names the mistake only if the fix gives the right answer.
Where the right answers come from
Nobody types the answers in. The formula engine works each one out from the lesson's own formula. A second, separate spreadsheet engine checks every lesson in our tests. How a lesson is built and checked has the rest.
New here? Lesson 1 is free and needs no account. It takes about ten minutes.