A first order reaction has k = 4.62 × 10⁻³ s⁻¹…

Step 1. Half-life. $t_{1/2} = \dfrac{0.693}{4.62 \times 10^{-3}\ \text{s}^{-1}} = 150\ \text{s}$.

Step 2. The number of half-lives. $10\ \text{min} = 600\ \text{s}$, and $\dfrac{600\ \text{s}}{150\ \text{s}} = 4$.

Step 3. The share left. $\left(\tfrac{1}{2}\right)^4 = \tfrac{1}{16} = 6.25\ \%$.