I am working on this Physics question and I don't understand why the answer is what it is.

Here is the question:

40. Computer chips (Fig. 1-13) etched on circular silicon wafers of thickness 0.300 mm are sliced from a solid cylindrical silicon crystal of length 25 cm. If each wafer can hold 100 chips, what is the maximum number of chips that can be produced from one entire cylinder?

Here is the book's solution:

\f40. Multiply the number of chips per wafer times the number of wafers that can be made from a cylinder. 100 chips 1 wafer 250 mm chips 83, 000 wafer 0.300 mm 1 cylinder cylinder