This approach is being taught to kids in india.This is called vedic mathematics. simple mental Mathematics.. Harry is a genius who spread memory systems...He is great.
564 + 435 is 999, so it's just one multiplication problem when it's all added together (326 x 999). 326 x 1000 = 326,000, and if you subtract 326 x 1 (which is just 326), then you have the answer. 326,000 - 326 = 325,674. It's easy to do mentally. I would subtract 300, then 20, then 6, and say to myself, "325,700, 325,680, 325,674". This method is known as working to the nearest zero.
In other words, Lorayne is demonstrating a math trick, not a math skill. Summing the two multiplications looks like an added difficulty, but actually invents an escape route to a difficult task. Notice he didn't write each of the two products until it was _read_ to him.
Once he had the two copies of 326 and the 564, he subtracted the 564 from 999 so that's why he used 435. To come up with the sum of the two products is simply 326 times (564+435) or 326 times 999. 999 is, of course, 1000-1 so now the problem is 326 times (1000-1) or 326 times 1000 minus 326 times 1, which is just 326. Now we know we're at 326,000 - 326 and it's a simple subtraction problem.
