ADD UP TRICK
Charles decided to impress his dad. ‘Write down any random seven figure number please, then write down any other seven figure number under the first one.’ His dad did this.
‘Now I will write one more number, and then I want you to write down another one, then I will write a second,’ said Charles. This was the result:
Dad’s first number – |
7,258,391 |
Dad’s second number – |
1,866,934 |
Charles’s first number – |
2,741,608 |
Dad’s third number – |
5,964,372 |
Charles’s second number – |
8,133,065 |
‘Right,’ said Charles, ‘I bet I can add these numbers up in less than five seconds.’ ‘Nonsense, even with a calculator you couldn’t do it that quickly,’ said his dad. But in three seconds Charles had written down the answer to the sum, which was 25,964,370. How did he do it?