Men suddenly become quiet when solving a math problem

Maybe they're concentrating

It's called thinking. I know women claim to be able to multitask, but really that's just not applying yourself fully to either of the tasks.
:o)

Yes. It's normal. I believe everyone does it. People can be analytical and it's not dependent on gender? I sometimes write down the formula or progress and close my eyes to reflect on how I arrived there.

Hey, sometimes people stare out into space if they need to for concentration.

are they engineers by any chance ? :D

Yes it's normal. Analytical women do the same thing when solving math problems. That kind of problem solving is not gender dependent.