Question

Difficulty: MediumOverlapping Sets and Inclusion-Exclusion Principle

A corporate venture capital firm evaluated 120120 technology startups for investment. Each startup met at least one of three key criteria: strong artificial intelligence capability, established revenue growth, or international market presence. Exactly 6565 startups met the artificial intelligence criteria, 5555 met the revenue growth criteria, and 5050 met the international presence criteria. Furthermore, 2525 startups met both the artificial intelligence and revenue growth criteria, 2020 met both the revenue growth and international presence criteria, and 1515 met both the artificial intelligence and international presence criteria. How many startups met all three investment criteria?

  1. A
    55
  2. 1010Answer
  3. C
    1515
  4. D
    2020
  5. E
    2525

Answer

The number of startups that met all three investment criteria is 10.
According to the Inclusion-Exclusion Principle for three sets, the total population is equal to the sum of the three individual sets minus the sum of the three pairwise intersections, plus the intersection of all three sets. Substituting the given values: 120=65+55+50(25+20+15)+x120 = 65 + 55 + 50 - (25 + 20 + 15) + x, which simplifies to 120=110+x120 = 110 + x, giving x=10x = 10. Thus, 1010 startups met all three criteria.

Step-by-Step Solution

1
State the Principle of Inclusion-Exclusion for three sets
ABC=A+B+C(AB+BC+AC)+ABC|A \cup B \cup C| = |A| + |B| + |C| - (|A \cap B| + |B \cap C| + |A \cap C|) + |A \cap B \cap C|
To account for startups counted in multiple overlapping categories without double-counting or over-subtracting.
2
Substitute the known values from the problem statement into the formula
120=65+55+50(25+20+15)+x120 = 65 + 55 + 50 - (25 + 20 + 15) + x, where x=ABCx = |A \cap B \cap C|
Every startup meets at least one criterion, so the union size equals the total number of startups (120120).
3
Simplify the sums and solve for xx
120=17060+x    120=110+x    x=10120 = 170 - 60 + x \implies 120 = 110 + x \implies x = 10
Subtracting 110110 from 120120 gives the exact number of startups meeting all three criteria.

Key Concept

Three-Set Inclusion-Exclusion Principle
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