"It's not rational to treat 2+2 as 5." — logical as contrasted to illogical
"I know you're upset, but please think about this in a rational manner." — based on reason as contrasted to emotion
"When I was 10-years-old, I wasn't very smart, but I was still rational." — capable of using reason as contrasted to being insane or lacking the ability to reason
"In matters of the heart, I trust my intuition more than my rational analysis." — based on a logical analysis as contrasted to intuition, instinct, custom, tarot-card reading, or some other system of decision making
Those whose attitude towards the war is most nearly rational are the subject peoples of the disputed territories.
rational = reasonable
There are no more uses of "rational" in 1984 by Orwell.