The second question: peering at the towering seven-layer tower, the red dots of light double on each level, make up a total of three hundred and eighty-one. How many lights are on each floor?
The problem is asking how many lamps there are on each of the seven-layer tower, where the number of dots on the lower floor is twice that of the upper floor, and the total red lamps known sum up to three hundred and eighty-one.
With hardly any deliberation, Li Xuan could quickly calculate the answer in his mind.
x+2x+4x+8x+16x+32x+64x=381
Therefore, there were three lamps on the seventh layer, six lamps on the sixth, twelve lamps on the fifth, twenty-four on the fourth, forty-eight on the third, ninety-six on the second, and one hundred and ninety-two on the first.
Li Xuan robustly wrote the answer on the rice paper: "Give me the third question!"
