Very carefully...
No you don't use your whole brain. Only part of your brain is ever used.
about 10%
You already use 100% of your brain. It is a myth that we don't. See related question, "Why can't people use 100% of their brains ?" Also related link.
100% all humans do.
Being alive would be sufficient to use 100% of your brain, however you don't nor would you want to use 90% of your brain at once.
100%. Its a myth that we only use 10%. If we only used 10% we would be brain dead.
You always use 100% of your mind (brain). There is an old wives' tale that says we only use 10% but that isn't true.
Probably 100 percent, because if you become a Buddha you achieved maximum level of consciousness
No, people use 100% of their brains. It is a common myth that we only use 10% of our brains.
We use a 100% all the time no matter what even when sleeping.
100% everyone uses. You use it 100% everyday. Eating, dreaming, walking, talking, using electronics etc.
unfortunately we already are using all of our "brain cells". we have no extra brain, despite the popular misconception.