The amount of meat needed can be calculated using the concept of direct proportion. If the caterer needs 40 pounds of meat for 25 guests, we can set up a ratio to find out how much meat is needed for 100 guests.
First, we determine the amount of meat per guest:
\[ \text{Meat per guest} = \frac{40 \text{ pounds}}{25 \text{ guests}} = 1.6 \text{ pounds per guest} \]
Now, we can calculate the amount of meat needed for 100 guests:
\[ \text{Meat for 100 guests} = 100 \text{ guests} \times 1.6 \text{ pounds per guest} = 160 \text{ pounds} \]
Therefore, the caterer should order 160 pounds of meat for 100 guests.