Three friends each pack a bag for a trip. Mandy's bag is 20% heavier than Kathleen's bag. Donna's bag is 25% lighter than Kathleen's bag. By what percent is Mandy's bag heavier than Donna's bag?

Mandy's bag is 60% heavyer than Donna's.

Step-by-step explanation:

When someone's bag is "x%" heavyer then someone else's it's the same as saying that it is "100% + x%" of that value, while if it is lighter it's the same as saying that it is "100% - x%".

Since Mandy's bag is 20% heavier than Kathleen's, then:

Mandy = 1.2*Kathleen

Since Donna's bag is 25% lighter than Kathleen's, then:

Donna = 0.75*Kathleen

Kathleen = Donna/0.75

Then

Mandy = 1.2 * (Donna/0.75) = 1.6*Donna