Spectrum #74: Order these metals by density — the solution
The Spectrum puzzle from October 27, 2026: six things on one hidden scale, lightest to densest, with every figure and where the checks were best spent.
The puzzle
Order these metals by density, lightest at the top and densest at the bottom. The board opened in this order:
- Lead
- Silver
- Iron
- Gold
- Lithium
- Aluminum
Iron was already in place; Lead opened 4 places from home.
The walkthrough
The ends first. Lithium is the lightest of the six at 0.53 g/cm³ and Gold the densest at 19.3 g/cm³. Anchor those and the middle four are what is left to place.
Where the scale splits. The widest gap is between Lead (11.3 g/cm³) and Gold (19.3 g/cm³) — 8 g/cm³ apart. Everything above that line belongs on the lightest side and everything below it on the densest side, so sorting the six into those two groups is most of the puzzle.
The closest call. Silver (10.5 g/cm³) and Lead (11.3 g/cm³) are only 0.8000000000000007 g/cm³ apart — the pair that is a coin flip without the figures, and the place to spend a check: a check locks whatever is already right and leaves only the wrong tiles to swap.
The answer
| # | Lightest to Densest | Figure |
|---|---|---|
| 1 | Lithium | 0.53 g/cm³ |
| 2 | Aluminum | 2.7 g/cm³ |
| 3 | Iron | 7.9 g/cm³ |
| 4 | Silver | 10.5 g/cm³ |
| 5 | Lead | 11.3 g/cm³ |
| 6 | Gold | 19.3 g/cm³ |
Previous: Spectrum #73 (Mon, Oct 26) · Next: Spectrum #75 (Wed, Oct 28) · All Spectrum solutions
About Spectrum
Spectrum is Noggin’s daily ordering puzzle: six things, one hidden scale, three checks. Tiles in the right place lock green; the figures turn over when the board is done. How to play Spectrum, or play today’s.