To determine the feed conversion efficiency (FCE) of the poorest weight gainer among the four farm animals (P, Q, R, and S), we first need to understand what feed conversion efficiency means. FCE is a measure of how effectively an animal converts feed into body weight gain. It is calculated using the formula: [ \text{Feed Conversion Efficiency (FCE)} = \frac{\text{Weight Gained (kg)}}{\text{Feed Consumed (kg)}} ] Step-by-Step Calculation

1. Calculate FCE for Each Animal:
2. Animal P:
   • Feed Consumed = 50 kg
   • Weight Gained = 20 kg
   • FCE = ( \frac{20 \text{ kg}}{50 \text{ kg}} = 0.4 )
3. Animal Q:
   • Feed Consumed = 90 kg
   • Weight Gained = 30 kg
   • FCE = ( \frac{30 \text{ kg}}{90 \text{ kg}} = 0.3333 ) (approximately 0.33)
4. Animal R:
   • Feed Consumed = 100 kg
   • Weight Gained = 25 kg
   • FCE = ( \frac{25 \text{ kg}}{100 \text{ kg}} = 0.25 )
5. Animal S:
   • Feed Consumed = 150 kg
   • Weight Gained = 30 kg
   • FCE = ( \frac{30 \text{ kg}}{150 \text{ kg}} = 0.2 )
6. Identify the Poorest Weight Gainer:
7. Now, we compare the FCE values calculated:
   • P: 0.4
   • Q: 0.33
   • R: 0.25
   • S: 0.2
8. The poorest weight gainer is Animal S, with an FCE of 0.2.

Conclusion The feed conversion efficiency of the poorest weight gainer (Animal S) is 0.2. Therefore, the correct answer is D. 0.2. Explanation of Other Options

• Option A (0.4): This is the FCE for Animal P, which is the best weight gainer, not the poorest.
• Option B (0.33): This is the FCE for Animal Q, which is better than Animal S.
• Option C (0.25): This is the FCE for Animal R, which is also better than Animal S.

Common Pitfalls

• Misidentifying the Poorest Gainer: It's crucial to compare the FCE values correctly to identify the poorest weight gainer.
• Rounding Errors: When calculating FCE, ensure that you maintain precision, especially when dealing with decimals.

Revision Summary

• Feed conversion efficiency (FCE) measures how well animals convert feed into weight gain.
• FCE is calculated using the formula: ( \text{FCE} = \frac{\text{Weight Gained}}{\text{Feed Consumed}} ).
• The poorest weight gainer among the animals is identified by comparing their FCE values.
• The correct answer for the poorest weight gainer's FCE is 0.2 (Animal S).