Defined model

A drop in a garden pool

Probability:
9.26 × 10⁻⁷%
Odds:
1 to (1.08 × 10⁸)
dBan
−80.3 dBan

Even in this garden pool, mark one drop-sized portion and a uniform choice returns to it only once in 108 million on average.

Calculation

V = 6 × 3 × 1.5 × 1,000 = 27,000 L; drop volume = 0.25 mL = 0.00025 L; p = 0.00025 / 27,000 = 1 / 108,000,000

Assumptions

The garden pool is an illustrative rectangular model, 6 m long and 3 m wide, with a water depth of 1.5 m. The adopted 0.25 mL faucet-drop estimate comes from USGS. The water volume is partitioned conceptually into equal drop-sized portions, and one is selected uniformly. One portion is designated in advance.

Sources

  1. USGS Water Science School: how much water does a dripping faucet waste? 2019 faucet-drop estimate: 0.25 mL per drop, within a stated 0.2–0.333 mL range
  2. Geometric example model