What primary school did you go to, where you had to multiply those kinds of numbers in your head?
RE your second paragraph, it's easier than it sounds. 637 is an awkward number, we'll start by rounding up to 640: 640 * 2 = 1280, anyone in tech knows 2x that is 2560. Make up the missing 3: 3 * 4 = 12, 2560 - 12 =…
What primary school did you go to, where you had to multiply those kinds of numbers in your head?
RE your second paragraph, it's easier than it sounds. 637 is an awkward number, we'll start by rounding up to 640: 640 * 2 = 1280, anyone in tech knows 2x that is 2560. Make up the missing 3: 3 * 4 = 12, 2560 - 12 =…