Egypt, like China, is one of the four ancient civilizations. Ancient Egyptians only used scores with numerator 1, such as 1 / 3 + 1 / to represent 2 / 5, 1 / 4 + 1 / 7 + 1 / 28 to represent 3 / 7, and so on. Now there are 90 Egyptian scores: 1 / 2, 1 / 3, 1 / 4, 1 / 5,... 1 / 90, 1 / 91. Can you pick out 10 of them, plus the sign, is their sum equal to - 1?

Egypt, like China, is one of the four ancient civilizations. Ancient Egyptians only used scores with numerator 1, such as 1 / 3 + 1 / to represent 2 / 5, 1 / 4 + 1 / 7 + 1 / 28 to represent 3 / 7, and so on. Now there are 90 Egyptian scores: 1 / 2, 1 / 3, 1 / 4, 1 / 5,... 1 / 90, 1 / 91. Can you pick out 10 of them, plus the sign, is their sum equal to - 1?

I'll tell you a formula that you can set by yourself. I'm also a junior one student. This problem is very simple. You can start from - 1. It's very simple