The number of significant digits in 0.001001 is :-

Options

A. 6
B. 4
C. 7
D. 2

Answer

To determine the number of significant digits in the number 0.001001, we can follow these steps:

### Step 1: Identify the leading zeros
Leading zeros (the zeros before the first non-zero digit) are not considered significant. In the number 0.001001, the leading zeros are the three zeros before the digit '1'.

**Hint:** Ignore any zeros that come before the first non-zero digit when counting significant figures.

### Step 2: Locate the first non-zero digit
The first non-zero digit in 0.001001 is '1'. This is the starting point for counting significant digits.

**Hint:** Look for the first digit that is between 1 and 9 to begin counting significant figures.

### Step 3: Count all significant digits from the first non-zero digit
After the first non-zero digit '1', we have the digits '0', '0', and '1'. All these digits are significant.

- The '1' is significant.
- The first '0' after '1' is significant.
- The second '0' after '1' is also significant.
- The last '1' is significant.

**Hint:** All digits after the first non-zero digit, including zeros, are significant if they are between non-zero digits or come after a non-zero digit in a decimal number.

### Step 4: Total the significant digits
Now we count:
- The first '1' (1 significant digit)
- The first '0' after '1' (1 significant digit)
- The second '0' after '1' (1 significant digit)
- The last '1' (1 significant digit)

Adding these together gives us a total of 4 significant digits.

**Final Answer:** The number of significant digits in 0.001001 is **4**.

### Summary of Steps:
1. Identify leading zeros (not significant).
2. Locate the first non-zero digit.
3. Count all digits from the first non-zero digit onwards as significant.
4. Total the significant digits.