including 4 different news journals, 5 different entertainment magazines and 6 different comic books
If 3 publications are picked, where some of them are of the same type, how many combinations are there?
2. There are 12 different junior form textbooks and 16 different senior form textbooks. How many ways are there to arrange 4 junior form and 6 senoir form text in a row on the bookshelf? (give the answer correct to 3 sig. fig. and scientific notation)
更新1:
ans 1. 335 2. 1.44 x 10^13