easier way to do permutation, combination and binomial probability ?

[dentalstudent2021]

Hi,
I am using Destroyer for math and they have the equations for permutations, combination etc... but I am not sure if I will be able to remember these.

is there a method to solve these without memorizing these formulas....and are these tested a lot ?

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[cacajuate]

Did you watch chads videos for math?

 

[DAT Destroyer]

Hi,
I am using Destroyer for math and they have the equations for permutations, combination etc... but I am not sure if I will be able to remember these.

is there a method to solve these without memorizing these formulas....and are these tested a lot ?

For combinations : nCr = n!/(n-r)!r!
Permutations: nPr = n!/(n-r)!

Remember that when order matters,we use permutations and when it's not we use combination.
For permutations ABC is different BAC than CAB etc.... Because the order of the letters matter. For a combination ABC is the same as BAC etc....
As far as doing probabilities you just have to read the question carefully. The wording of the question is very important.

For example : what is the probability of picking a green and a white marble? And
What is the probability of picking a green then a white marble?
These 2 questions ask different things. The first asks to pick a green and a white in any order. The second asks for a green first then a white marble.

There are only 2 formulas you need to remember one for combination one for permutation. The most important thing is know when to use what. And the best way to remember them is practice practice practice. Math Destroyer has a lot of these type of problems.

Hope this helps!