Give the step-by-step reasoning process and then the final answer. Alice wants 1000 folded paper cranes. She folds half by herself, and a friend folds a fifth of the remaining paper cranes for her. How many paper cranes does Alice still need to fold?
Alice folds 1000 * 0.5 = 500 paper cranes by herself. This leaves 1000 – 500 = 500 paper cranes left to fold. A friend folds a fifth of the remaining amount, so they have folded 500 / 5 = 100 paper cranes for her. This means there is a total of 1000 – 500 – 100 = 400 paper cranes left for Alice to fold.
The final answer: 400.