Division Tips and Tricks
So you're trying to work out a division problem in your head. Your palms are sweaty. Your heart is racing. The Jeopardy theme song is playing in your head - da, da, da, da, da, da, daaaaaa - Chill out already! KW's got a few tips and tricks to give you a head start. Check 'em out!
Division Tips - Dividing By OneThis one's a cinch. You wanna divide a number by one, do you? Easy. Take the number - say 1,372 - and that's it. That's your answer. 429 � 1 = 429. 11 � 1 = 11. 1,000,000 � 1 = 1,000,000. And you thought this was hard? Phhhh.
Division Tips - Dividing By TwoWhen you divide something by two, you simply cut it in half. Half of 234 is 117, therefore 234 � 2 = 117. Let's try a smaller number: 20 � 2 = 10. Why? Because half of 20 is 10. If the number you're trying to divide is odd (like, say, 33), then you can't divide it evenly by two. Easy peasy.
Division Tips - Dividing By ThreeWanna know if you can divide a number evenly by three? Just add up all the digits until you have a single number. If THAT number is divisible by three, so is the original number. Case in point: 8787. If you add 8+7+8+7 you get 30. Then add 3+0, which equals three. Three is definitely divisible by three, so you know that 8787 is too.
Division Tips - Dividing By FourThe rule for dividing by four is the same as for dividing by two - only you have to do it twice. If you want to divide 88 by 4, you simply halve 88 (which is 44) and then halve that number (which, in this case, is 22). 12 � 4? Half of 12 is six and half of six is three - so your answer is three.
Division Tips - Dividing By FiveIf you want to know whether a number can be evenly divided by five you just need to look at the number's last digit. If the last digit is a zero or a five, then the number is divisible by five. 1,573,740 ends in zero so it is divisible by five. Since 23 ends in three, it isn't divisible by five.
Division Tips - Dividing By SixIf a number is BOTH divisible by three (see the three rule) AND an even number (ending in 0,2,4, 6 or 8) then it is divisible by six too. 312 is an even number and if you add up all the digits they equal six, which is divisible by three. Therefore 312 is divisible by six.
Division Tips - Dividing By SevenTo find out if a number is divisible by seven, take the last digit, double it, and subtract it from the rest of the number. "Huh?" you may be saying. Check out this example: If you had 203, you would double the last digit (three) to get six, and subtract that from 20 (the remaining amount) to get 14. Since 14 is divisible by seven, 203 is too.
Division Tips - Dividing By EightThis brings us back to the old halving trick we used with two and four. Try halving four times to get the answer to this one. Want an example? Okay. 64 � 8. Half of 64 is 32 and half of 32 is 16, then half of 16 is 8. Therefore 64 � 8 = 8.
Division Tips - Dividing By NineUse the same trick we used to see if a number is divisible by three - it works for any power of three (3,6,9,12, etc.).
Division Tips - Dividing By TenIf a number is evenly divisible by 10 it will end in zero. Simply remove that zero to find out what that number would be if it were divided by 10. Example: 370 � 10 = 37 (which is 370 with the "0" taken off the end). 50 � 10 = 5. See the pattern here?