Mathbound
Sign up

Daily puzzle · 2026-10-19 · Divisibility

Mathbound Daily Puzzle — 2026-10-19 — Divisibility Solution

Level 3

Compute ∑k=1150⌊150k⌋\displaystyle\sum_{k=1}^{150}\left\lfloor\frac{150}{k}\right\rfloor.
  1. A.752
  2. B.781
  3. C.778
  4. D.22500
  5. E.780

Answer: E

Key idea: Dirichlet hyperbola method / equal-floor blocks.

Set it up: Sum floors for N=150N=150.

Solution: 780780.

Browse more archived puzzles · Try today's puzzle

Mathbound Daily Puzzle — 2026-10-19 — Divisibility Solution