 # Stephen Downes

Knowledge, Learning, Community
Honestly, you shouldn't need a calculator to be able to figure out percentages. It's easy. I'll show you how, where a small number (say 13365) is a percentage of a big number (say 456312):
- Divide your big number by 100. Eg. if it's 456312 you now have 4563.
- How many times does that go into your small number? Eg., how many times does 4563 go into 13365?
- If that's too difficult, divide each number by 10 and round off until it becomes simple. How many times does 456 go into 1336? Still too hard? How many times does 46 go into 137? Still too hard? How many times does 5 go into 14? Just under 2.5.
- Sure, it's a bit ballpark, because of the rounding (the actual percent in the example is 2.93 percent, which is actually near the outer edge of the margin of error for this method). But you can do it in about 5 seconds in your head.
- if you need more precision, proceed stepwise, calculating 1 significant digit each time you divide by 10, and keeping the remainer for the next step. Like so: 4563 goes into 13365 2 times; 456 goes into the remainder (4339) 9 times, etc., giving you 2.9

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