How to get the other side

Jenny, Rose and Michael must cross a river to visit their friend David who lives on the other side. They have a boat; but they also have a problem.
Jenny and Claire each weigh 50 kilograms and Michael weighs 75 kilograms. The boat will carry only 100 kg at a time!

"Oh no! We can't all get across the river!" moans Rose.

Jenny thinks for a moment and says: "I know how we can all get across. It will just take more than one trip!"

What is Jenny's plan?

The above problem is a variation of the classic problem of the man with his wolf, goat and cabbage:

"A man wishes to cross a river with his wolf, goat and cabbage. He has a rowing boat but it it is only big enough for him and one other object. The wolf will take any chance to eat the goat and the goat wants to eat the cabbage. How can the man get all three objects across safely?"

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