Mental Arithmetic and the Abacus

Doing arithmetic in your head is something you should work on, because it's often useful for working out whether you have enough money to buy two or more items, or to work out if a one-for-the-price-of-two offer is actually better value than a two-for-the-price-of-three offer on the same product. It also helps you perform much better with things like the Countdown Numbers Game. It may be that mental arithmetic skills are never tested in important exams in the country where you live, but don't limit yourself by the low expectations of your country: you should work at all these skills regardless.

There is a simple trick you can use when faced with a sum like 34 + 48. If you add 2 to the 48 it becomes a much easier number to add to the 34: you can easily add 50 on in your head, getting 84, and then you can take the 2 away again to get the right answer. Alternatively you could ignore the 4 in 34 and just add 30 to the 48 (getting 78) and then add on the 4: that's the other way round from the way you would do it on paper. However, the Asians have a much better way of doing sums in their heads, and it involves an imaginary abacus: just take a look at this video.