For fractions like 1/3rd and 1/4th all it takes is common sense.
English says "1/4", or "1 over 4", or "1 quarter".
Japanese says "4 bun no 1", or the practical equivalent of saying "4 under 1" in English.
I consequently routinely say the numbers in reverse, confounding both myself and anyone around me before I realize my brain engaged in furious tentacle sex with the numbers.
1/5th pound burger is going to sell better than the quarter pounder while using less beef.
The vast majority of processing is happening outside language-related areas of the brain. There's certainly leaky interfaces between areas of the brain, but if you literally thought in a language, and that distinction persisted throughout the brain, that would seem to imply that speaking 3 languages would require 3x the number of connections in the brain.
The strong Sapir-Whorf hypothesis would presumably be true if we literally thought in a language, but the strong form of the Sapir-Whorf hypothesis has been thoroughly discredited.
In other words, "thinking in a language" is an illusion.
Tangentially, I realised in high school that I was doing almost all math operations as word transformations. I reasoned this was why even familiar procedures for which I confidently & consistently got correct results were taking substantially longer than everybody else. I was translating everything twice.