A percent is not magic. It is a ratio.
“By how many percent more did you spend compared to last week?” = (new − old) / old. Then cell format percent. With grades watch out — a lower grade is better, growth “up” on a grade 1→3 is worse, not better.
The Modeller calculates changes that a chart then shows as a story.
Week-to-week spending
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On
Kapesneyou have SUM of spending in C2:C8. In F10 writeSpending this week, G10=SUMA(C2:C8). -
In F11
Last week (by hand), G11 e.g.180— last week you wrote it somewhere else or an estimate. -
F12
Change %, G12:=(G10-G11)/G11Format G12 Percent. 0.15 = 15% spending increase.
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When G11 = 0, division by zero #DIV/0! Handle it:
=KDYŽ(G11=0;"—";(G10-G11)/G11) -
On the survey: E2 count of rolls. F2
Share:=E2/SUMA($E$2:$E$5)Format percent. Total of shares = 100%.
Inside the cell 0.2 = 20% on screen. Do not write 20 and format % → 2000%. You already know that from Chart maker.
Grades — careful with “growth”
This year’s average B8 vs. last month in G15 (by hand 2.0). Change:
=(B8-G15)/G15
When the average drops from 2.0 to 1.8, that is an improvement, but the percent comes out negative. In the 메모 column write: “negative % = better grades”.
What often goes wrong
Division by zero. Always KDYŽ or a check of the denominator.
Percent vs. percentage points. Average from 2.0 to 1.8 = −0.2 points, not −10% points without context. Be clear in the label.
A share without $ in the denominator. =E2/SUMA(E2:E5) drifts when you copy. SUMA($E$2:$E$5).
🏫 Grade average — trend
Save the average every month into a small table Month | Average. A line chart from it — Modeller + Chart maker. Percent change between months in a side column.
💰 Pocket money — reserve in %
F1 = 0.1 → 10% reserve. G12 shows by how many % this week beat last — a different question than the reserve. Do not mix both percents in one sentence without a label.
📊 Class survey — vote share
Share column next to Count. Sentence under the chart: “Roll 36% (8/22).” Number from E and F, not by eye.
🏆 Mini dashboard — one percent
On the dashboard max one percent visible — say the share of the survey winner or reserve 10%. More percents = a mess.
Now you 💪
First: spending change week vs. week in G12 with protection against division by zero.
Second: a Share column on the survey D:E.
Check: Percents formatted. Shares total 100%. Negative change on grades explained.
What to take from this lesson
- Change % = (new − old) / old, percent format.
- Handle division by zero with KDYŽ.
- Share = part / whole, $ in SUMA of the whole.
© 2026 Ing. Martin Polak / AlgoRhino · 콘텐츠 이용 약관