Chapter 7 - Similarity - 7-1 Ratios and Proportions - Practice and Problem-Solving Exercises - Page 436: 11

$\frac{10}{17}$ or 10:17

Convert each measurement to mm Diameter of a table tennis ball: 40 mm Diameter of a tennis ball: 6.8 cm = 68 mm This gives you the proportion of $\frac{40}{68}$. Reduce by dividing the numerator and denominator by 4 Resulting in $\frac{10}{17}$. This can also be written as 10:17