# Five rows repeat. Only three should be removed.

Suppose a workshop list contains these six rows:

| Learner | Workshop |
| --- | --- |
| A | Mapping |
| A | Mapping |
| B | Charts |
| C | Tables |
| C | Tables |
| C | Tables |

How many duplicate rows are there? The question sounds numerical, but it is missing a policy. It might mean rows belonging to repeated groups, distinct repeated groups, or excess copies to remove.

For this exercise, define an exact duplicate as identical values in both columns. Retain one copy of every distinct row. With that policy, three rows are removed: one extra A/Mapping and two extra C/Tables. Three distinct rows remain.

Five rows belong to repeated groups. That count includes the copies we intend to keep, so deleting five would answer a different question. Two groups repeat, but counting those groups does not count the excess rows inside them.

The distinction becomes more important when the second column changes. Imagine K1/draft and K1/final. The identifier repeats, but the full rows differ. If the state represents a meaningful version, removing a row because its identifier repeats could discard information. The counting rule does not authorize deletion.

Before computing, finish these three statements:

1. The unit I am counting is a row, group, identifier or person.
2. Two records count as the same when these specific fields match.
3. The output is a count, a proposed edit or a retained dataset.

Then test a group of three identical records. Under a keep-one policy it contributes two removable rows, not three and not one. This small control catches two common misunderstandings without requiring a large spreadsheet.

All identifiers here are fictional. Skill Path's [twelve data-reasoning exercises](https://skills.editorialdeskmedia.com/guides/skills-data-reasoning-exercises) extend the same habit to weighted averages, missing values and conditional percentages. Each exercise provides assumptions, optional hints and an explained answer. Try the question before opening the answer; repeating the same numbers does not demonstrate transfer to a new dataset.

Editorial note: Drafted with AI using original synthetic exercises. Arithmetic is checked; educator review and measured learning outcomes have not been obtained. Exercise text, tables and answer keys in the linked package carry their stated CC BY 4.0 license.