To multiply two 2digit numbers without showing work, first multiply the ones digits together, then 'crossmultiply,' and finally multiply the tens digits together. Make sure to carry whenever a product exceeds 9. As you will see in the examples below, you must work your way from right to left to perform this trick. Example 1: 12 x 23
Example 2: 31 x 24
Note: This trick will also work on numbers with zeroes and decimal points. Also as you are crossmultiplying, it is generally easier to begin with the larger product and then add the smaller product. A percentage is a way of expressing a number as a fraction of 100 (per cent meaning “per hundred” in Latin). It is often denoted using the percent sign, “%”, or the abbreviation “pct”. For example, 45% (read as “fortyfive percent”) is equal to 45/100, or 0.45. Percentages are used to express how large/small one quantity is, relative to another quantity. The first quantity usually represents a part of, or a change in, the second quantity, which should be greater than zero. For example, an increase of $ 0.15 on a price of $ 2.50 is an increase by a fraction of 0.15/2.50 = 0.06. Expressed as a percentage, this is therefore a 6% increase. Remember that:
Example: Let's consider the number 50.
Example 1: 105 x 105
This works for all numbers up to 150 but is more useful if the number is close to 100. It also works for numbers smaller then 100 but in that case you simply have to subtract the difference to 100 from your number. Example 2: 96 x 96
The following video is giving you some more examples and also shows what happens for larger distances. 
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