You could also replace % with 10⁻² and use scientific notation: 0.72% ⋅ 0.03% = 0.72 ⋅ 10⁻² ⋅ 0.03 ⋅ 10⁻² = 7.2 ⋅ 10⁻³ ⋅ 3 ⋅ 10⁻⁴ = 7.2 ⋅ 3 ⋅

You could also replace % with 10⁻² and use scientific notation: 0.72% ⋅ 0.03% = 0.72 ⋅ 10⁻² ⋅ 0.03 ⋅ 10⁻² = 7.2 ⋅ 10⁻³ ⋅ 3 ⋅ 10⁻⁴ = 7.2 ⋅ 3 ⋅ 10⁻³ ⋅ 10⁻⁴ = 21.6 ⋅ 10⁻⁷ = 2.16 ⋅ 10⁻⁶ ≈ 2 in 1 million