Exercise · ZW-STEINER-TRIPLE-SYSTEM-007 · ★★☆ Intermediate
In an \(\mathrm{STS}(v)\), how many blocks pass through a fixed point if \(v=13\)?
Choose one option.
Show answer
- D. 6
Explanation
With \(r=\frac{13-1}{2}=6\) blocks per point. Answering 12 uses \(v-1\) instead of \((v-1)/2\), and 78 is the total number of pairs.
Review the concept: Steiner triple system
A Steiner triple system \(\mathrm{STS}(v)\) is a block design in which \(v\) points are grouped into triples so that every pair of distinct points lies in exactly one triple.
\[b=\frac{v(v-1)}{6},\quad r=\frac{v-1}{2}\]
More practice problems: steiner triple system
- ZW-STEINER-TRIPLE-SYSTEM-001 How many pairs of distinct points does a set of v points contain?
- ZW-STEINER-TRIPLE-SYSTEM-002 How many pairs does a block of size 3 cover in a Steiner triple system?
- ZW-STEINER-TRIPLE-SYSTEM-003 If v=7, how many blocks does an STS(7) have?
- ZW-STEINER-TRIPLE-SYSTEM-004 How many blocks contain each point in an STS(9)?
- ZW-STEINER-TRIPLE-SYSTEM-005 Which value of v is required for a Steiner triple system to exist?
- ZW-STEINER-TRIPLE-SYSTEM-006 An STS(v) has b=35 blocks. What is the value of v?
- ZW-STEINER-TRIPLE-SYSTEM-008 How many blocks does an STS(13) have?
- ZW-STEINER-TRIPLE-SYSTEM-009 An STS(v) has r=6 and b=26. Is v=13 the only possible value, and what about v=12? Justify using the…
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