The value of `124.2 - 52.487` with due regard to significant places is

Options

A. 71.7
B. 71.71
C. 72
D. 71

Answer

To solve the problem of finding the value of `124.2 - 52.487` with due regard to significant figures, we can follow these steps:

### Step 1: Perform the Subtraction
First, we need to calculate the difference between the two numbers:
\[ 124.2 - 52.487 \]

### Step 2: Calculate the Result
Now, we perform the subtraction:
\[ 124.2 - 52.487 = 71.713 \]

### Step 3: Identify Significant Figures
Next, we need to determine the number of significant figures in each of the original numbers:
- The number `124.2` has **4 significant figures** (the digits 1, 2, 4, and the decimal point indicates that the 2 is significant).
- The number `52.487` has **5 significant figures** (all digits are significant).

### Step 4: Determine the Limiting Significant Figures
When performing subtraction, the result should be reported with the same number of decimal places as the measurement with the least number of decimal places. Here, `124.2` has **1 decimal place** (the digit after the decimal is 2), while `52.487` has **3 decimal places**.

### Step 5: Round the Result
Since the result `71.713` needs to be rounded to **1 decimal place** (due to `124.2`), we look at the first digit after the decimal point, which is `7`. The digit after `7` is `1`, which is less than 5. Therefore, we do not round up.

Thus, rounding `71.713` to **1 decimal place** gives us:
\[ 71.7 \]

### Final Answer
The value of `124.2 - 52.487` with due regard to significant figures is:
\[ \boxed{71.7} \]

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