As an example of the above, I think grade school math tests should maybe place less and less emphasis on deriving perfectly-accurate-right-down-to-the-ones-digit when it comes to arithmetic, and place more and more emphasis on the ability to make quick and intuitive guesstimates. If you need the perfect answer upon which the water supply of the East Bay area will rely, then you best break out the calculator. If you're at a retail shop and trying to figure out in your head if you can afford a T-shirt once you account for the sale price and your coupon, then you just need a quick and reliable ballpark figure.

I'm sure my fellow poker players can really get the above point: when do you ever actually break out the pencil and paper and do long division right down to the final decimal place? When you're at the table, you need quick mnemonics to make vague apple-to-kinda-apply comparisons; when you're studying and want to get the numbers just right, you have like 5 tabs open with different tools that instantaneously spit out perfectly derived data.