How to Add

Step 3 See subtractions

This is a similar technique to borrowing ones, but can be extended to numbers other than one. If you tried to do 98+97 using traditional means there would be a lot of carries. The easier way to do this addition is to recognise that 98 = (100-2) and 97 = (100-3) so the result is the sum of these, namely (200-5) or 195. Many people can do this intuitively given a case like 99+99=198, but with a little practise you can make it much more general by recognising larger subtractions. The result may become very confusing if the subtractions sum to more than 10 (for instance, 93 + 94 = 200 - 13), so beware of replacing an awkward addition with an equally awkward subtraction.

Pros: general, work with large numbers
Cons: needs a conceptual shift, requires some practise