Solution to the Problem of time for finding out unevenly distributed points

The problem is as follows:There are two unevenly distributed fragrances. The burning time is one hour. How can you determine a period of 15 minutes?

A subtle difference:There are two unevenly distributed fragrances, each of which is burned for an hour. How can you determine a period of 15 minutes?

First of all, I don't know where the question comes from. Then, after the question is circulated, there are few words missing in key areas, and many students will finally be puzzled.

If the total time for burning two incense sticks is one hour, the method is to split the two incense sticks into two halves. The four incense sticks both ends at the same time, and the burning is 15 minutes.

It is assumed that the two incense types are a, B, a + B = 60, and divide them by 4 in 15 minutes. Then a/4 = A/2 × 1/2, and B is also true. N/2 is equal to a two-head burn, and it needs to be done twice as fast.

If each piece is burned for an hour, it is spread on the Internet to burn both ends, and burn another segment at the same time, so that the first 30 minutes, the remaining 30 minutes are 15 minutes.

PS: Is this the same as a typical Math Problem in elementary school?