Question: A historian of astronomy has 6 ancient star charts, 2 of which are from the 1st century and 4 from the 2nd century. How many distinct arrangements are there if charts from the same century must be grouped together?

Sun, 03 May 2026 14:43:22 +0000

**How Many Unique Ways Can Astronomical Star Charts Be Arranged When Century Groups Matter?** Curious about ancient sky maps—how many distinct orders exist when 6 star charts, shaped by history’s dual centuries, must be displayed together with like centuries grouped? This question is quietly gaining interest among history and astronomy enthusiasts across the U.S., reflecting growing fascination with how ancient civilizations tracked the cosmos. Combining time periods continues to spark exploration in digital learning spaces, especially on platforms that prioritize meaningful discovery. The key to solving this puzzle lies in recognizing that century-based grouping transforms a simple ordering problem into one with meaningful structure. Rather than treating each chart as an individual item, the constraint groups the two 1st-century charts together and the four 2nd-century charts together—essentially treating each century’s set as a single unit first. ### The Two-Century Grouping Principle