no calculators, but you have scrap paper which should be an immense help.
The question you refer to...A plane at FL310 is instructed to descend to FL280, if the plane is descending at a rate of 1200 ft per minute, how long will the plane take to descend to FL280.
So we're interested in a descent of FL310 --> FL280, which is 3000ft.
If the plane is descending at 1200ft per minute, we need to divide 3000 by 1200.
2 x 1200, or 2 minutes, is 2400, leaving 600. You should be able to see that this is half of 1200
, which will then be 30 seconds. So 3000/1200 = 2.5, or 2 mins 30 seconds.
Simples, see? There are a lot of questions where you will need maths like this, so get practicing!