Basic maths in testing

"I don't need Grammatics; I'm not on exams."
"I don't need math; I'm not in the market."
Unfortunately, You can hear the following words very often in the streets.

And I regularly hear words like "I'm a tester, I don't need maths in my job".

But you need it.

Here are some little effective tricks from basic math science that could help you at your work in testing and management.