速算法

1. 4,281 x 11 becomes the following digits: (4)(4+2),(2+8)(8+1)(1) or 47,091

When the sum of a pair is greater than 10, carry that digit to the next left pair (as seen above, where 2+8 was 10)

2. Let's try something harder. 9,621,576,521 x 11 becomes: (9)(9+6),(6+2)(2+1)(1+5),(5+7)(7+6)(6+5),(5+2)(2+1)(1) or 105,837,341,731