Utah Community Learning

Plus, minus, times, divide, and pointing at other cells

Okay sooo. Last time we did SUM and I basically would not shut up about it. Today we're widening out. Because addition is great but it's not the only math you've got, and once you see how the pointing part works, you can do all four.

Here's the thing. A formula in a spreadsheet is really just two ideas stacked together: pick an operator, and point at cells instead of typing numbers. Once that clicks, the rest is just which symbol you use.

The equals sign is the whole trick

Every formula starts with =. That's how the sheet knows you're not just typing a number or a word, you're asking it to calculate something.

Then you build it out with these:

+ for adding
- for subtracting
* for multiplying
/ for dividing

So =4+4 gives you 8. Not exciting yet. The exciting part is next.

Point at cells instead of typing numbers

Say you've got a number in A1 and a number in A2. Instead of typing =4+4, click into A3, type =, then click on A1, type +, then click on A2, hit enter.

You'll see =A1+A2 show up in the formula bar. That's it. That's the whole move.

Why does this matter more than it sounds like it should? Because now if you change the number in A1, A3 updates on its own. You didn't retype anything. That's the entire point of this module, right there in one sentence. If you're typing the same number into two places, you've already made a future mistake, you just haven't met it yet. It's just a matter of when you find it.

Try all four at home

Open a blank-ish sheet, or use one you've already got going.

Put a number in A1, a number in A2.
In A3, type =A1+A2 and hit enter.
In A4, type =A1-A2 and hit enter.
In A5, type =A1*A2 and hit enter.
In A6, type =A1/A2 and hit enter.

Now go change the number in A1. Watch all four update at once. That little jolt of "oh, it just did that" is basically why I do this for a living.

One real caution here: if A2 is zero and you're dividing, you'll get an error that looks like #DIV/0!. That's not broken, that's the sheet correctly telling you dividing by zero doesn't work. Don't panic, don't retype the whole formula, just go check what's in that cell.

You can mix operators too

You're not stuck picking just one. =A1+A2*A3 is a real formula. Just know that multiplication and division happen before addition and subtraction, same order of operations you did in school and possibly resented. If you want to force a certain part to happen first, wrap it in parentheses: =(A1+A2)*A3.

I'm not gonna pretend I always remember the order without thinking about it. When I'm not sure, I just add parentheses around the part I mean first. Costs nothing, saves a headache.

A quick aside on being confidently wrong

Not gonna lie, I fact-check myself a lot doing this job, because it's real easy to sound sure about something you're actually fuzzy on. Had a coworker once tell me flat out that VLOOKUP can't look to the left of its search column, like it was gospel. He was wrong about the actual mechanism, there's a way around it, but here's the thing, he was right that it's a pain and most people don't bother. I told him so. Both things were true at once. I bring that up because formulas are one of those spots where it's easy to nod along like you get it and then go home and just retype numbers anyway. If a formula's not doing what you expected, that's not you being bad at this, that's the normal way you find out what a formula actually does.

Fixing a wrong pointer

If you click the wrong cell while building a formula, don't start over. Just click into the formula bar, delete the wrong cell reference, and click the correct cell instead. The sheet doesn't care that you fumbled it. Neither should you.

This is also a good excuse to leave something broken on screen if you're practicing with someone else, a partner, a kid, whoever, and ask them to find where the pointer's aimed wrong. It's a genuinely good way to learn this. Way better than watching me do it clean.

Before next time

Build one small formula at home that points at two real numbers you care about, groceries, gas, whatever you've got sitting in a sheet already. Change one number and watch it ripple through. That's the whole lesson, just make it happen with your own stuff once.