Plan from the supplied facts
Fictional eligible audience is U1–U5. Proposed cohort A contains U1,U2,U3; B contains U3,U4. Reach after both is their union. Membership here is a planning list, not evidence that a user has actually received or used the release.
| Cohort | Members | Size | New versus A |
|---|---|---|---|
| A | U1,U2,U3 | 3 | 3 initial |
| B | U3,U4 | 2 | 1: U4 |
| Union | U1,U2,U3,U4 | 4 | U5 still outside |
Work through the choice
3+2−1 overlapping member=4 unique users. The overlap is U3; adding sizes directly counts that user twice.
What fraction of the eligible list is planned to be reached after both cohorts?
Show the worked answer
4/5=80%. U5 is the one eligible member not in either cohort.
Material to use in your plan
Keep cohort membership sets, overlaps, unique union and eligible denominator. Track actual exposure separately when rollout starts.