The problem of unit 1 will be applied to many mathematical problems. In mathematics, the unit 1 refers to a whole concept. For example, in the problem, we don't know how long a certain amount and a certain time are, so we can regard this amount and this time length as the unit of 1.

It is worth noting that the unit 1 will never change as a whole. We just regard it as a whole, not that it is only 1 copy.

For example:

Now we don't know the construction quantity, so let's say that the total construction quantity is 1. If Team A has completed the construction for 6 hours, then we can divide the total amount by 6 with the unit 1, and we can get that the efficiency of Team A in this whole is 1/6.

For another example, we don't know how many pages a book has, so we regard it as a unit of 1. It is understood that Xiao Li finished reading this book in 8 hours. Then, by dividing the integer of 1 by the speed of 8 hours, we can get that his reading speed is 1/8.