Official Solution:Robert can eat a 20 kg bag of potatoes in 10 days. If, together with his wife Jane, they can eat the same bag in 8 days, how many days does it take for Jane to eat a 20 kg bag of potatoes by herself?A. 80
B. 40
C. 20
D. 16
E. 10
Since Robert can eat a 20 kg bag of potatoes in 10 days, he can eat 2 kg of potatoes per day. Hence, in 8 days, he can eat 16 kgs, which means that Jane can eat 20 - 16 = 4 kg in the same 8 days or 1/2 kg per day.
Therefore, to eat a 20 kg bag of potatoes by herself, it would take her \(\frac{20}{\frac{1}{2} }\) = 40 days.
Answer: B