In the previous article, we have discussed Python Program to Find Strong Numbers in a List

**Arithmetic progression:**

An Arithmetic progression is a mathematical sequence of numbers in which the difference between the consecutive terms is constant.

In general, an arithmetic sequence looks like this: a, a+d, a+2d, a+3d,…………….

where a = first term

d= common difference

**Formula** : d= second term – first term

Given an Arithmetic series, and the task is to find the missing term in the given series.

**Examples:**

**Example 1:**

**Input:**

Given Arithmetic Progression series = [10, 14, 18, 22, 30]

**Output:**

The missing term in the given Arithmetic Progression series is: 26

**Example 2:**

**Input:**

Given Arithmetic Progression series = [100, 300, 400, 500, 600, 700]

**Output:**

The missing term in the given Arithmetic Progression series is: 200

## Program to Find the missing term of any Arithmetic progression

Below are the ways to find the missing term in the given Arithmetic progression series.

### Method #1: Using For Loop (Static Input)

**Approach: **

- Give the list ( Arithmetic Progression series) as static input and store it in a variable.
- Calculate the length of the given series using the built-in len() function and store it in another variable.
- Calculate the common difference by finding the difference between the list’s last and first terms and divide by N and store it in another variable.
- Take a variable, initialize it with the first term of the given list and store it in another variable say “first term”.
- Loop from 1 to the length of the given list using for loop.
- Inside the loop, check if the difference between the list(iterator) and “first term” is not equal to the common difference using if conditional statement.
- If the statement is true, print the sum of “first term” and common difference
- Else update the value of variable “first term” by iterator value.
- The Exit of the program.

**Below is the implementation:**

# Give the list ( Arithmetic Progression series) as static input and store it in a variable. gvn_lst = [100, 200, 400, 500, 600, 700] # Calculate the length of the given series using the built-in len() function # and store it in another variable. lst_len = len(gvn_lst) # Calculate the common difference by finding the difference between the list's last and # first terms and divide by N and store it in another variable. commn_diff = int((gvn_lst[lst_len-1]-gvn_lst[0])/lst_len) # Take a variable, initialize it with the first term of the given list and store # it in another variable say "first term". fst_term = gvn_lst[0] # Loop from 1 to the length of the given list using for loop. print("The missing term in the given Arithmetic Progression series is:") for itr in range(1, lst_len): # Inside the loop, check if the difference between the list(iterator) and "first term" # is not equal to the common difference using if conditional statement. if gvn_lst[itr]-fst_term != commn_diff: # If the statement is true, print the sum of "first term" and common difference print(fst_term+commn_diff) break else: # Else update the value of variable "first term" by iterator value. fst_term = gvn_lst[itr]

**Output:**

The missing term in the given Arithmetic Progression series is: 26

### Method #2: Using For Loop (User Input)

**Approach: **

- Give the list ( Arithmetic Progression series) as user input using list(),map(),input(),and split() functions and store it in a variable.
- Calculate the length of the given series using the built-in len() function and store it in another variable.
- Calculate the common difference by finding the difference between the list’s last and first terms and divide by N and store it in another variable.
- Take a variable, initialize it with the first term of the given list and store it in another variable say “first term”.
- Loop from 1 to the length of the given list using for loop.
- Inside the loop, check if the difference between the list(iterator) and “first term” is not equal to the common difference using if conditional statement.
- If the statement is true, print the sum of “first term” and common difference
- Else update the value of variable “first term” by iterator value.
- The Exit of the program.

**Below is the implementation:**

#Give the list ( Arithmetic Progression series) as user input using list(),map(),input(),and split() #functions and store it in a variable. gvn_lst = list(map(int, input( 'Enter some random List Elements separated by spaces = ').split())) # Calculate the length of the given series using the built-in len() function # and store it in another variable. lst_len = len(gvn_lst) # Calculate the common difference by finding the difference between the list's last and # first terms and divide by N and store it in another variable. commn_diff = int((gvn_lst[lst_len-1]-gvn_lst[0])/lst_len) # Take a variable, initialize it with the first term of the given list and store # it in another variable say "first term". fst_term = gvn_lst[0] # Loop from 1 to the length of the given list using for loop. print("The missing term in the given Arithmetic Progression series is:") for itr in range(1, lst_len): # Inside the loop, check if the difference between the list(iterator) and "first term" # is not equal to the common difference using if conditional statement. if gvn_lst[itr]-fst_term != commn_diff: # If the statement is true, print the sum of "first term" and common difference print(fst_term+commn_diff) break else: # Else update the value of variable "first term" by iterator value. fst_term = gvn_lst[itr]

**Output:**

Enter some random List Elements separated by spaces = 100 300 400 500 600 700 The missing term in the given Arithmetic Progression series is: 200

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