He gave the 2 students the numbers in advance.
It's an easy tell.
First, no 2 boys that young are going to rattle off a number that fast yet they instantly responded. The second kid couldn't sound more deflated if he tried yet he was on the ball to respond lol.
Second, the odds of the 2 numbers adding up to 999 are 1,998 to 1 - what a lucky guy!
Thirdly, when writing the answer he never looks at the digits he wrote on the board - even out of habit i still glance at numbers.
Fourthly, he is writing an answer to a number left to right whereas an older guy like him should be writing right to left because he is working out an exact 6 figure answer.
Fifthly, his explanation is based around multiplying by 1,000 and then deducting 1 x 428..... which he briefly stumbles explaining lol. Give him 2 numbers that add up to something like 613 and he won't be able to do it.
It's better to teach maths using real world scenarios to keep people interested. This 'trick' is pretty lame and his class participation reflects that.
