**How Many Permutations Are Possible With Four Numbers?** – **There are 10,000 possible combinations of four numbers when each number is used multiple times.** There are also 5,040 possible four-number combinations when each number is used only once.

How come? There are ten options, ranging from zero to nine, for each number in the combination. Due to the fact that there are four numbers in the combination, there are a total of 10 possible combinations for each of the four numbers. Thus, the number of possible combinations is 10*10*10*10 or 104, or 10,000.

The formula for the binomial coefficient is a general method for calculating the number of combinations. The number of combinations of k elements from a set containing n elements is denoted by n!/(k!*(n-k)!, where the exclamation mark indicates a factorial. Need to go into greater detail? We have you covered.

Read more: How Many Ounces Equal 2/3 Cup?

## Formula for Combination count

A straightforward equation can be used to calculate the number of possible four-number combinations. Consider each number as an individual and each position in the combination as a seat. Each seat can only accommodate one person, and there are a total of 10 seats available. (There are ten numbers because numbers with a single digit range from 0 to 9)

In any given combination, any of the ten numbers can occupy any of the four available positions. There are ten options for the first seat in any given combination. In addition, there are 10 options for the second seat in any given combination. The same holds true for the third and fourth seats as well.

Multiply the number of options for the first seat by the number of options for the second seat by the number of options for the third seat by the number of options for the fourth seat to find the total number of options for all combinations.

In other words, multiply 10 by 10 by 10 by 10 by 10. In the end, you will discover that there are 10,000 possible four-number combinations.

## Number of Combinations Formulas for Non-Repetitive Numbers.

If you claim that there are 10,000 possible four-number combinations, you would be both correct and incorrect. Thus, the answer of 10,000 allows any of the ten numbers to occupy any of the four seats. One of the 10,000 possible combinations could be 1111, 0000, 2222, or 3333, according to this theory. Let’s add a twist to the equation.

In the real world, four-digit combinations are typically devoid of repeated digits. In fact, many companies prohibit the use of four-digit passwords that consist of repeated numbers. How many possible four-digit number combinations do not contain repeated digits?

Forget about the seats for a moment and consult the binomial coefficient formula, a handy mathematical formula. The following is the formula:

## The expression n!/(k! x (n-k)!)

In case you were unaware, each exclamation point denotes a factorial. Although both the name and the formula appear to be complicated, the process is actually quite simple. It turns out that the concept of people seated will also be useful here. “K” represents the number of people who can sit in any given seat, and “n” represents the number of seats each of those people can occupy.

In the case of determining the number of combinations of four numbers, k equals 10 and n equals 4. The equation is as follows:

4!/(10! times (4-10)!

Without entering into factorials, this reduces to:

10 by 9 by 8 by 7 equals 5,040

Do you detect a pattern here? In the first seat, any one of the ten digits may sit. Now, only nine numbers remain to occupy the second seat. With one more number eliminated, there are only eight remaining candidates for the third seat, and only seven candidates for the fourth seat.

See? The binomial coefficient is much simpler than it initially appears. With the binomial coefficient, any number selected for one seat is eliminated from consideration for the remaining seats. This roughly halves the total number of possible combinations.

## What This Reveals About Your Mobile Device Password

Let’s be truthful. Unless youâ€™re really, really into numbers, you probably didnâ€™t search just to find out the number of possible combinations of four digits. In reality, youâ€™ve probably found your way to this corner of the internet because youâ€™re trying to set a four-digit password. And itâ€™s very commendable that youâ€™re giving thought to your passcode.

Four-digit passwords can seem pretty simple since they are some of the shortest passwords youâ€™re likely to use. However, they also tend to be some of the most important. You may use four-digit number combinations to open your phone or to log in to certain apps more quickly, but where else do you use four number combinations? Most banks ask customers to select a four-digit PIN in order to authorise transactions and use ATMs.

Hackers take advantage of the fact that four-digit number combinations are used as passwords for things you probably care a lot less about protecting than your bank card PIN. People are not nearly as creative with passwords as they ought to be. If someone can decipher the code on your phone’s lock screen, it’s likely that they can also authorise a transaction using your debit card, since there’s a high likelihood that the numbers are identical.

Banks also do not help the situation. As a result of the fact that many banks permit repeating numbers, individuals frequently have 10,000 PIN options. If your bank is more security-aware, you will only have 5,040 possible combinations to select from. Numerous individuals employ four-digit combinations that are either repetitive or sequential. For instance, 1234 is a very common selection, and some individuals combine the same number repeatedly, such as 1111 or 2222.

Avoid wasting your knowledge of the binomial coefficient. There are literally tens of thousands of possible combinations of four numbers. Do not simply select your birth year or date. Please, for the love of all that is good, do not choose 1234. If you want to keep a particular person’s prying eyes away from your smartphone, you’ll have to work much harder than that. Choose your passwords carefully to protect your identity (and data).