Find out the missing term in the series `"………..",7999,26999,63999,124999`.

Answer

To find the missing term in the series `"………..", 7999, 26999, 63999, 124999`, we will analyze the pattern in the given numbers.

### Step 1: Identify the given terms
The series is:
- Missing term (let's denote it as X)
- 7999
- 26999
- 63999
- 124999

### Step 2: Analyze the differences between the terms
Let's calculate the differences between the consecutive terms:

1. Difference between 124999 and 63999:
\[ 124999 - 63999 = 61000 \]

2. Difference between 63999 and 26999:
\[ 63999 - 26999 = 37000 \]

3. Difference between 26999 and 7999:
\[ 26999 - 7999 = 19000 \]

### Step 3: Identify the pattern in the differences
The differences we calculated are:
- 61000
- 37000
- 19000

Now, let's see if there's a pattern in these differences:
- The difference between 61000 and 37000:
\[ 61000 - 37000 = 24000 \]

- The difference between 37000 and 19000:
\[ 37000 - 19000 = 18000 \]

### Step 4: Predict the next difference
If we observe the differences:
- The first difference is 24000
- The second difference is 18000

This suggests that the differences are decreasing. If we follow this pattern, we can assume the next difference will be:
\[ 19000 - 6000 = 13000 \]

### Step 5: Calculate the missing term
Now, we can find the missing term (X) by subtracting 13000 from 7999:
\[ X = 7999 - 13000 = -5001 \]

However, since we are looking for a positive term, we need to re-evaluate our calculations.

### Step 6: Correct the approach
Let's analyze the original series again:
- The series seems to be based on cubes of numbers minus one.

1. For 124999, we can see that:
\[ 125000 - 1 = 124999 \quad (\text{which is } 50^3 - 1) \]

2. For 63999:
\[ 64000 - 1 = 63999 \quad (\text{which is } 40^3 - 1) \]

3. For 26999:
\[ 27000 - 1 = 26999 \quad (\text{which is } 30^3 - 1) \]

4. For 7999:
\[ 8000 - 1 = 7999 \quad (\text{which is } 20^3 - 1) \]

### Step 7: Find the missing term
Following this pattern, the missing term should be:
\[ X = 1000 - 1 = 999 \quad (\text{which is } 10^3 - 1) \]

### Final Answer
The missing term in the series is **999**.

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