Today's advice will teach you what I consider the most powerful math trick in the world. You can solve almost anything with it and I can teach it to you very easily. If you master it you will have a big advantage over other students and get many more problems correct on tests.
It is all about units and the method is called Dimensional Analysis. The key is to understand that units cancel if divided by themselves.
meter / meter = nothing, since you are cancelling out the units.
kg / ounce X ounce /kg = nothing
You just draw lines through any units that are divided by the same unit. However, leave any numbers in front of it alone.
We can now apply it and solve what would otherwise be a very tough problem very simply.
Example: Convert 25 kg to ounces
Step 1. Put down whatever you know.
We also know 1 ounce = 28 g and 1000 g = 1 kg
Just arrange what you know so what is left are the final units and your answer will "magically" appear.
25 kg X 1000 g / 1 kg
Don't do any math until you get the final units you want, which are ounces in this example. We now just have grams (g), so continue the unit cancelling.
25 kg X 1000 g / 1 kg X 1 ounce / 28 g
We are now done! The answer is 25 X 1000 / 28 = 892.9 ounces
Another example. How many seconds are in 4 hours?
You know 60 s in a minute, 60 min in an hour
4 hours X 60 min / 1 hour X 60 s / 1 min = 4 X 60 X 60 = 14,400 seconds
It takes all the guesswork out of math and makes very tough problems routine. You won't ever make the mistake of not knowing which number goes on the top during a conversion step, since only one spot will make things cancel. People will think your are a "genius" at math with this system. I was near the bottom in my math class before learning it and quickly got top scores in the most advanced level at school after learning it.
Truly one of the greatest math techniques in the world. It works because the things you are multiplying, like 1 ounce / 28 g, are all equal to '1' because they are the same thing on the numerator and denominator.