Jenny is trying to lose weight and has decreased her
energy intake by 250 kcal per day. how long should it
take her to lose 1 lb of body fat?

14 days

Explanation:

Jenny's goal is to lose weight. When a person loses weight, that means the person needs to have more calories burned/expelled than calories consumed. The person may also restrict her calorie intake and in Jenny's case, this is her method of losing weight. She decreased her energy intake by 250 kcal per day.

Remember that in order to lose 1 lb of fat, one needs to lose 3,500 kcal/calories.

Thus, we can divide 3,500 kcal/calories by 250 kcal per day in order to know how long it will take for Jenny to lose weight.

Thus: 3,500 kcal ÷ 250 kcal/day = 14 days

This means, Jenny needs 14 days in order to lose 1 lb of body fat.