Is there a faster way to multiply by 11? What about 14? Let's take the following example: 1412 x 14 = 19768 The technique helps you finding digits from left to right as following: take the first digits of 1412…
Find the square of a number (nearing to 100) in head
How much is 5 ² ? How about 12 ² ? Well, if you have already finished the gymnasium then maybe you are already used to find the square for these numbers. But how about 104 ² ? I found…
Fast multiplication n-digits (on certain situations)
I've found a solution for fast multiplication n digits with respect to the following conditions: have the same number of digits the first digit of both numbers are equal the sum of last digit of both numbers is 10 Example…
Fast multiplication by 11
One of my favourite techniques is that which allows us to fast multiplication by 11. To get your attention I will say that I can multiply in my head the following numbers: 748346274 x 11 = 8231809014 The technique is…
Fast multiplication 3 digits
Are you scared when comes to multiply a product like 123 x 321 in your head? Well, that's not so hard as it seems to be! Fast multiplication 3 digit For this we can use a technique which reduce the…
Fast multiplication 2 digits
How do you calculate how much is 93 x 97 in your head? Sounds that impossible? There are many quick algorithms depending on the nature of the numbers you want to multiply. In some situations fits better one algorithm, in…