Which is the correct volume reading combination: 6.6 mL and 2.3 mL?

• A. 6.6 mL and 2.0 mL
• B. 6.7 mL and 2.0 mL
• C. 6.7 mL and 2.3 mL
• D. 6.6 mL and 2.3 mL

Answer: (D)

Reading volumes comes down to reporting to the smallest division your measuring instrument allows and keeping the same level of precision for all readings. If the instrument’s scale is marked to 0.1 mL, you should record readings like x.y mL, with that tenths place shown and the digit before it not altered unless the actual measurement justifies it.

The valid combination uses 6.6 mL for the first measurement and 2.3 mL for the second because both are to the tenths of a milliliter, matching the instrument’s precision. Rounding the first to 6.7 mL or the second to 2.0 mL would introduce unnecessary rounding and misrepresent what the scale shows. If you were to add them, you’d typically report the sum with the same precision, e.g., 8.9 mL.