Identify the molecular formula of thyroxine from the given structure
Thyroxine has the formula: $\mathrm{C_{15}H_{11}I_4NO_4}$ So, it contains 4 iodine atoms.

Calculate molar mass of thyroxine

Using the given atomic masses:

• Carbon: $15 \times 12 = 180$
• Hydrogen: $11 \times 1 = 11$
• Iodine: $4 \times 127 = 508$
• Nitrogen: $1 \times 14 = 14$
• Oxygen: $4 \times 16 = 64$

Therefore, total molar mass: $180 + 11 + 508 + 14 + 64 = 777$

Mass of iodine in one mole of thyroxine $4 \times 127 = 508$

Percentage of iodine $\%\text{ iodine} = \frac{508}{777} \times 100$

$\%\text{ iodine} \approx 65.38\%$

Nearest integer $\boxed{65}$

Comparison with stored answer
Stored correct answer = $65$
Derived answer = $65$
Hence, they agree.