Final answer:
The mass of an object measured with a triple beam balance by adding the readings of 100 grams from the first beam, 40 grams from the second beam, and 7.2 grams from the third beam is 147.2 grams.
Step-by-step explanation:
To determine the mass of an object using a triple beam balance, you add the readings from all three beams. In this case, if the first beam reads 100 grams, the second reads 40 grams, and the third reads 7.2 grams, you simply add these values together to find the total mass.
Addition of the values from the beams:
100 g (first beam) +
40 g (second beam) +
7.2 g (third beam) = 147.2 grams.
Therefore, the mass of the object is 147.2 grams, which corresponds to option A.