Help needed: Prove the following proposition.

[swift dawn]

What is the name of this book?

[sturdy hound]

Split the numbers into 2 parts
1-100 and 101-200
now
for any # of numbers in the set that are between 1-100, you have to take at least the same amount from the 101-200 list
because there's guaranteed to be at least one multiple of a number in 1-100 in 101-200
so this thus
there are, if x represents the # of numbers used from 1-100:
x + (100-x) = 100 numbers to choose that do
not divide each other. this is less than 101
proof

[royal lodge]

Easy mode: at least one number must be even.

That's all you need

[low elk]

I'm going through the same book

It does explain how to do it, do you just want a hint?