To find the mass of one tennis ball, you can divide the total mass of the three balls by the number of balls.
The total mass is \( 6 \frac{3}{10} \) grams, which can also be expressed as an improper fraction.
First, convert \( 6 \frac{3}{10} \) to an improper fraction:
\[ 6 \frac{3}{10} = \frac{6 \times 10 + 3}{10} = \frac{60 + 3}{10} = \frac{63}{10} \text{ grams} \]
Now, divide this by 3 to find the mass of one ball:
\[ \text{Mass of one ball} = \frac{63}{10} \div 3 = \frac{63}{10} \times \frac{1}{3} = \frac{63}{30} \]
Now simplify \( \frac{63}{30} \):
The greatest common divisor (GCD) of 63 and 30 is 3, so:
\[ \frac{63 \div 3}{30 \div 3} = \frac{21}{10} \]
This can also be expressed as a mixed number:
\[ \frac{21}{10} = 2 \frac{1}{10} \text{ grams} \]
Thus, the mass of one tennis ball is \( 2 \frac{1}{10} \) grams or \( \frac{21}{10} \) grams.