# Permutation Calculations – how to do quickly?

Are you worried about solving Permutation Problems and you want to do Permutation Calculations quickly? This article will enable you to do Permutation Calculations quickly and easily.

When you encounter a Permutation problem on the SAT Test, the greatest challenge for you is to do Permutation Calculations correctly and quickly.

Remember, in Mathematics sections of the SAT test you have to solve each SAT Math question in 75 seconds (average time). It is possible only when you know how to do calculations including Permutation Calculations easily and quickly. Here, we’ll tell you how to do Permutation Calculations in less than a minute so that you can save time for other SAT questions.

In order to do Permutation Calculations quickly you must be able to write Permutation equation correctly. Writing a correct Permutation equation is quite an easy task.

Permutation Calculations involves two variables. If you are able to recognize these two variables in given SAT Math question then you can write correct Permutation equation. Once you have written correct Permutation equation you are able to do quick Permutation calculations.

Every Permutation Problem asks you to arrange n items in group of r.  Recognize these two variables (n and r) and write Permutation equation to do Permutation Calculations.

Read the SAT Math question carefully and pay attention to how many items (n) are to be arranged in group of how many items(r).

Example

There are three doors to a class room. In how many ways can a student enter the room from one door and leave from the other door.

Solution

See that 3 doors are to be arranged in a group of 2 (1 for entry and 1 for exit) and entering from door A and leaving from door B is not the same as entering from door B and leaving from door A. It means order is important here or AB≠BA. So it is a math Permutation Problem.

Here n = 3 and r = 2

Now we write Permutation equation or Permutation Formula to perform Permutation Calculations.

P = n! / (n – r)!

= 3! / (3 – 2)!

= 3! / 1!

= (3 x 2 x 1) /1

= 6

At first glance, you will consider these Permutation Calculations difficult but by making practice you will be able to do Permutation Calculations in less than a minute.

Time Allocation

Reading and understanding the Permutation Problem = 15 seconds
Identifying n and r = 10 seconds
Writing Permutation equation or Permutation Formula = 10 seconds
Permutation Calculations = 25 seconds

If you do first step correctly then you can definitely solve math Permutation Problem quickly by performing Permutation Calculations within 25 seconds.