Imagine an HIV test that is 95% accurate (false positive rate of 5%) and around 2% of the tested population is infected with HIV. What is the probability that you actually have HIV when your test comes back positive?

What’s the simplest way to make 20 using only three 3s (no other digits) and a combination of mathematical operations using any of these symbols?

+ – × / ^ ! √ . ()

A dad offered to pay his son $5 for every correct answer on his math test. His son said he would pay his Dad $8 for every incorrect answer. There were 26 questions on the test and no money was exchanged.

How did this happen?

Without changing the order of these numbers, how can they equal 100?

3 5 6 2 54 5

What cheese is made backwards?