Final answer:
Jan's cat is heavier than Carl's cat, weighing 4,000 grams compared to Carl's cat's 2,900 grams, after converting Jan's cat's weight from kilograms to grams.
Step-by-step explanation:
To determine whose cat is heavier between Jan's cat and Carl's cat, we need to compare their weights in the same unit. Jan's cat weighs 4 kg and Carl's cat weighs 2,900 grams. Since 1 kilogram is equal to 1,000 grams, we can convert Jan's cat's weight into grams to make the comparison easier.
Jan's cat: 4 kg × 1,000 grams/kg = 4,000 grams.
Now that both weights are in grams, we can see that Jan's cat weighs 4,000 grams, while Carl's cat weighs 2,900 grams.
Based on the comparison, Jan's cat is heavier than Carl's cat.