Spectrum #75: Order these elements by share of Earth's crust — the solution
The Spectrum puzzle from October 28, 2026: six things on one hidden scale, least to most, with every figure and where the checks were best spent.
The puzzle
Order these elements by share of Earth's crust, least at the top and most at the bottom. The board opened in this order:
- Oxygen
- Aluminum
- Sodium
- Silicon
- Iron
- Calcium
Nothing was in its place; Oxygen opened 5 places from home.
The walkthrough
The ends first. Sodium is the least of the six at 2.4% and Oxygen the most at 46%. Anchor those and the middle four are what is left to place.
Where the scale splits. The widest gap is between Aluminum (8.2%) and Silicon (28%) — 19.8% apart. Everything above that line belongs on the least side and everything below it on the most side, so sorting the six into those two groups is most of the puzzle.
The closest call. Calcium (4.2%) and Iron (5.6%) are only 1.4% 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
| # | Least to Most | Figure |
|---|---|---|
| 1 | Sodium | 2.4% |
| 2 | Calcium | 4.2% |
| 3 | Iron | 5.6% |
| 4 | Aluminum | 8.2% |
| 5 | Silicon | 28% |
| 6 | Oxygen | 46% |
Previous: Spectrum #74 (Tue, Oct 27) · Next: Spectrum #76 (Thu, Oct 29) · 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.