Correct proportion: $\frac{1000\ \text{g}}{1\ \text{kg}}=\frac{3750\ \text{g}}{x\ \text{kg}}$. Cross-multiply: $1000\cdot x=1\cdot 3750\Rightarrow x=3.75$ kg. Unit rate: $3750\ \text{g}\times\frac{1\ \text{kg}}{1000\ \text{g}}=3.75\ \text{kg}$; g cancels. Reasonableness: 3750 g is a few thousand grams, so a few kilograms; 3.75 kg makes sense.

Proportion method: $\frac{0.45\ \text{kg}}{1\ \text{lb}}=\frac{x\ \text{kg}}{150\ \text{lb}}$. Cross-multiply: $1\cdot x=0.45\cdot 150\Rightarrow x=67.5$ kg. Unit rate: $150\ \text{lb}\times\frac{0.45\ \text{kg}}{1\ \text{lb}}=67.5\ \text{kg}$; lb cancels. Reasonableness: kilograms should be less than pounds since 1 lb is less than 1 kg; 67.5 < 150.

Proportion method: $\frac{16\ \text{tbsp}}{1\ \text{cup}}=\frac{x\ \text{tbsp}}{2.5\ \text{cups}}$. Cross-multiply: $1\cdot x=16\cdot 2.5\Rightarrow x=40$ tablespoons. Unit rate: $2.5\ \text{cups}\times\frac{16\ \text{tbsp}}{1\ \text{cup}}=40\ \text{tbsp}$; cups cancel. Reasonableness: more tablespoons than cups since tablespoons are smaller; 40 is larger than 2.5.

Proportion method: $\frac{2.54\ \text{cm}}{1\ \text{in}}=\frac{x\ \text{cm}}{32\ \text{in}}$. Cross-multiply: $1\cdot x=2.54\cdot 32\Rightarrow x=81.28$ cm. Unit rate: $32\ \text{in}\times\frac{2.54\ \text{cm}}{1\ \text{in}}=81.28\ \text{cm}$; inches cancel. Reasonableness: centimeters should be larger number than inches because 1 in is more than 1 cm; 81.28 > 32.