To multiply two 2-digit numbers without showing work, first multiply the ones digits together, then 'cross-multiply,' 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

1. Multiply the ones digits: 1x4=4 (ones digits answer).
2. Cross-multiply and add: (3x4)+(1x2)=14 (use the 4 as the tens-digit answer, and carry the 1).
3. Multiply the tens digits, and add the 1: (3x2)+1=7 (hundreds-digit answer).
4. Combine: 744 (the answer).

Note: 
This trick will also work on numbers with zeroes and decimal points. Also as you are cross-multiplying, 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 “forty-five 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:

• 100% of a number is the SAME number.
  
• Less than 100% of a number makes the number SMALLER.
  
• More than 100% of a number makes the number LARGER.
  

Note that 200% of a number is the DOUBLE of the number and 300% of a number is the TRIPLE of the same number. 

Example: Let's consider the number 50.

• 100% of 50 is 50 (SAME)
• 200% of 50 is 100 (DOUBLE)
• 300% of 50 is 150 (TRIPLE)

Example: 225% of 24

• 200% of 24 is 48 (DOUBLE)
  
• 25% of 24 is one fourth of 24, that is to say 24 x 1/4 = 6
• 225% of 24 is the sum of 48 and 6, hence 54 

The video below shows an alternative method to calculate the percent of a number.

Example 1: 105 x 105

1. Determine the difference between 105 and 100, which is 5.
2. Add this number to 105, which is 105 + 5 = 110
3. Square the number in Step 1, that is 5^2 = 25
4. The answer is 11025

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

1. Determine the difference between 96 and 100, which is -4.
2. Add this number to 96, which is 96 + (-4) = 92
3. Square the number in Step 1, that is (-4)^2 = 16
4. The answer is 9216

The following video is giving you some more examples and also shows what happens for larger distances.