The number in the third column of row 2 is: 2×3=6.
The number in the fourth column of the third row is 3×4= 12.
.........................................
The number in row m and column (m+ 1) is m×(m+ 1).
Therefore, the number of rows of 20 and 2 1 is 20×2 1=420.
A. Self-study courses for marketing majors
Self-taught marketing college exam subjects:
Introduction to marketing:
This major trains sen