The wrong number of the sequence 4 9 19 39 79 169 319 is

Options

A. 169
B. 79
C. 39
D. 9

Answer

To determine the wrong number in the sequence 4, 9, 19, 39, 79, 169, 319, we will analyze the pattern of the sequence step by step.

### Step 1: Identify the differences between consecutive terms
Let's calculate the differences between each pair of consecutive terms in the sequence:

- 9 - 4 = 5
- 19 - 9 = 10
- 39 - 19 = 20
- 79 - 39 = 40
- 169 - 79 = 90
- 319 - 169 = 150

So, the differences are: 5, 10, 20, 40, 90, 150.

### Step 2: Identify the pattern in the differences
Now, let's analyze the differences we calculated:

- The first difference is 5.
- The second difference is 10 (which is 5 * 2).
- The third difference is 20 (which is 10 * 2).
- The fourth difference is 40 (which is 20 * 2).
- The fifth difference is 90 (which does not follow the pattern of doubling).
- The sixth difference is 150.

It appears that the differences are supposed to double each time. However, the jump from 40 to 90 does not follow this pattern.

### Step 3: Determine the correct number
If we follow the pattern, after 40, the next difference should be 80 (which is 40 * 2). Therefore, the next term after 79 should be:

79 + 80 = 159.

### Step 4: Identify the wrong number
Since the term after 79 is given as 169, which should actually be 159, we can conclude that 169 is the wrong number in the sequence.

### Final Answer
The wrong number in the sequence is **169**.

---