I was particularly good at mental arithmetic.

我特别擅长心算。

My fondness for mental arithmetic came in very handy.

我喜欢心算因为使用心算是很方便的。

At school I did three years of arithmetic in one. I was particularly good at mental arithmetic.

在学校我把三年的数学课程一年就学完了，我特别擅长心算。

But all these different examples beg the question of how this mental arithmetic actually happens.

但所有这些不同的例子都提出一个问题——心算是如何产生的。

Even if the presidential candidates know in their guts that they are being hypocritical, they cannot very well be kept busy the whole campaign doing mental arithmetic.

即使总统候选人知道自己正滑向伪善的深渊，但总不能让他们在整个竞选活动中不停地做心算来维持本能。