Whole+Numbers

=1. Palindromic Numbers= = = Palindrome are words, sentences or numbers that read the same forwards and backwards. Numbers that are not palindromes can be made palindromes by performing a process 'reverse and add'. Eg. To make 84 a palindrome, we reverse the digits to get 48, then add to the original number 84 + 48 = 132 132 + 231 = 363 It took 2 steps to make 84 a palindrome.

=2. Order of Operation= = = Rule 1: Addition and Subtraction are on par.In an expression involving addition and subtraction only, you can do either addition or subtraction first. Rule 2: : Work out powers and square roots. Rule 3: Multiplication and division must be done before addition and subtraction. Rule 4: When multiplication and division occurs one after another, working from left to right is always correct. Rule 5: Division has greater precedence over multiplication.When multiplication and division occurs one after another, we can choose to do division first but not the other way round.

Rule 6: If an expression contains brackets, the expression in the bracker must be fully simplifed before the brackets are removed.

=3. Checking Divisibility of Whole Numbers= = = = = Subtract it from your number. (Not including the last number) If the answer is a multiple of 7, your number also is. || If the answer is 0 or divisible by 11, so is the big number. || Subtract it from your number. (Not including the last number) If the answer is a multiple of 13, your number also is. || it to your number. (Not including the last 2 numbers) If the answer is a multiple of 19, your number also is. (If the answer is too big, continue using the method.) || Try this (you may use a calculator): Choose a digit from 2 to 9. Write it six times. For example, if 4 is chosen the number is 444 444. Divide the six-digit number by 33. Next divide the result by 37 and finally divide this last result by 91. What is the final result? Can you explain why it works?
 * Number || Divisibility Test ||
 * 2 || The last digit is 0, 2, 4, 6 or 8 ||
 * 3 || The sum of the digits in the number is divisible by 3. ||
 * 4 || The last two digits in the number is divisible by 4 ||
 * 5 || The last digit is 5 or 0. ||
 * 6 || The number is divisible by 2 and 3 ||
 * 7. || Take the last digit off your number and multiply it by 2.
 * 8 || The last three digits in the number is divisible by 8. ||
 * 9 || The sum of the digits in the number is divisible by 9. ||
 * 10 || The last digit is 0. ||
 * 11 || Put alternate + and - signsin front of each digit.
 * 12 || The number is divisible by 3 and 4. ||
 * 13 || Take the last digit off your number and multiply it by 9.
 * 14 || The number is divisible by 2 and 7. ||
 * 15 || The number is divisible by 3 and 5. ||
 * 19 || Take the last 2 digits off your number and multiply it by 4. Add
 * 20 || Take away the 0. If it is even, the number is divisible by 20. ||
 * 21 || The number is divisible by 3 and 7. ||
 * 22 || The number is divisible by 2 and 11. ||

Source: Murderous Math: Numbers, The Key to the Universe by: Kjartan Poskitt