When you are at an interview for a future pilot job opening, for example with a psychologist, you could face a request to calculate some pretty heavy numbers in your head, in a situation where you have no calculator, no paper to make notes on and you could be forced to do another physic assignment at the same time such as the tapping test.
A math question could be to add, subtract, multiply, divide or maybe find the result of a percentage of some number. It could involve two or more numbers.
Its not to see if you are a genius with math, that is not a request to become a pilot, but more if and how you handle stress and multitasking at the same time while trying to get you out of an uncomfortable situation with elements you haven't experienced or learned about before.
The psychologist will start out easy and you can compare a combined set of assignments involving talking, spelling and some easy math while exercising a physical task, with flying your aircraft while communicating with the tower and/or your copilot at the same time you are navigating into a beacon, and he/she will increase the level and end up stressing you to see how you cope with that too.
An example:
Now, 2 plus 2 is easy, even under stress. So is 5 times 8. But what if the question was to do 68 multiplied by 26 ?
Now, a lot of people would probably think: "That is not fair, I can't do that in my head, especially having to do other things at the same time that I have to stay focused on".
There are probably several ways to help you with such a question under those conditions, but I found that the key thing is to crunch large numbers into smaller bits, into bits that I easily can handle under stress. Just like you can't eat a whole cake in one bite, you have to eat it in pieces. Same thing with large or difficult numbers. You have to "play" with the numbers, be a bit creative, think how can I make these numbers more easy to handle.
Easy numbers to handle is for instance:

2. Two is easy, its easy to add and subtract and it either double or half a number in multiplying or dividing.

10. Ten is easy. Easy to add and subtract and easy to multiply or divide, because it just add or reduce the amount of zero's in the end, or digits if you will.

5. Five is easy, its the half of ten and its easy going 5101520....

25. Twenty five, one quarter of 100, an easy number as well.

100. One hundred, just like ten but with two zeroes.
So what about 68 x 26. Well lets play a bit with the numbers, here is how I thought the solution:
68 is close to 70, can I use that easy number compared to the 26 and fiddle a bit with the difference that will be left ?  No, not really, but what about 26, that is very close to 25, just one higher than 25, I keep that in mind that 26 is just one higher than 25, remember that extra one, remember that one.
Ok, and 25 is 1/4 of 100 or half of the half of 100. Remember that, 1/4 is a half of a half, a lot easier to half a given number twice, than thinking what the quarter value is of a given number. Hmm, what if we multiply 100 with 68, that is 6800 (just add two zeroes to 68), now I just need to reduce it to 1/4 of its value, or with a half of a half. So 6800 is going to 3400 (half of 6 and 8 is 3 and 4, half of zero is still zero) and then to 1700 (crunching 34 in to 30 and 4, then half of 30 is 15 and half of 4 is 2, just remember to add the 2 to 15 and you get 17). Now I am close, 68 times 25 equals 1700. And my number was 26, just one higher than the 25 I used, as I remembered. So I just need to add 68 to 1700, which is easy because 68 added to the two zeros in 1700 is 68, so the end result is 1768.
It might have taken me 30 seconds to do it and reading this on your screen, this might seem over the top to do (or silly). But trust me, by making the calculations very very simple instead of one impossible hard piece of math that you almost need to be Rainman to comprehend while having to do other stuff in a very stressful situation, you stand a better chance getting the right result without accidentally stopping your physical simultaneously task and still keeping capacity left to maintain some level of situational awareness.
