Letīs see who gets this one right..
You have 10 packages of cookies. In each package there are 10 cookies, where each cookie weighs 10 grams, totalling 100 grams in the package. But in one of 10 the packages, each cookie weighs 9 grams, totalling 90 grams.
Now, usings a scale like this
and weighing ONLY ONCE, how can you find the package that weighs 90 grams?