Answer :

To find the sum of the two measurements, 0.3500 and 0.036, while preserving the correct number of significant figures, follow these steps:

1. Determine the number of decimal places in each measurement:
- 0.3500 has four decimal places.
- 0.036 has three decimal places.

2. Perform the addition:
- Add the two measurements together:
[tex]\[ 0.3500 + 0.036 = 0.3860 \][/tex]

3. Identify the measurement with the least number of decimal places:
- The least number of decimal places in our given measurements is 3 (from 0.036).

4. Round the result to reflect the appropriate number of significant figures:
- Based on the decimal places of the measurement with the fewest (3 decimal places), we round our resulting sum to 3 decimal places.

Therefore, the sum of 0.3500 and 0.036, rounded to the correct number of significant figures, is:
[tex]\[ \boxed{0.386} \][/tex]