The addition rule
The question
| Sold | Left | Total | |
|---|---|---|---|
| Small | 14 | 6 | 20 |
| Large | 8 | 12 | 20 |
| Total | 22 | 18 | 40 |
What percent are Small OR Sold?
%
What percent are one or the other?
How it works.
Small: 20·Sold: 22
20 + 22 − 14=28
28÷40=70%
- 01
"OR" means EITHER is enough, so it covers the whole Small row and the whole Sold column. The row holds 20 and the column holds 22.
- 02
Adding them counts the corner cell TWICE — the 14 who are both Small and Sold are in the row and in the column. Subtract that overlap once.
- 03
So 28 of the 40 surveyed, which is 28 ÷ 40 = 70%.