If you ask the maximum discount, it is equivalent to asking the maximum discount rate, 30% off.
If you ask for the highest price, it is equivalent to asking for the biggest discount.
Suppose you buy x yuan,
The amount of goods purchased exceeds that of 200 yuan, but less than that of 500 yuan,
The discount rate is (x-60)/x =1-60/x.
The topic requires a maximum discount, which is equivalent to the maximum value of the formula (1-60/x).
The maximization formula (1-60/x) requires x to be larger, because the larger the denominator, the smaller the fractional value, and the smaller the fractional value subtracted, the greater the formula result.
Because x is restricted by conditions
When x=500, the result of the formula (1-60/x) is 0.88, but x can't be 500, so the result of the formula can only be infinitely close to 0.87999999. ...
Therefore, the maximum discount is 18% when the purchased goods exceed 200 yuan but are lower than 500 yuan.
When the goods purchased exceed 500 yuan, as above, when x is infinite, the result of the formula is infinitely close to 1.
The result of the formula is 0.999 ...
At this time, the maximum discount rate is 99%.
Has the problem of fifth grade in primary school really involved the infinite concept that only middle schools have? It's not an Olympic math problem, is it?