Find the least common denominator for the fractions in the list. \[ \frac{13}{35 r^{5}}, \frac{7}{20 r^{3}} \] The LCD is $\square$. (Simplify your answer.)

Step 1 ：The least common denominator (LCD) of two fractions is the least common multiple (LCM) of their denominators. In this case, the denominators are \(35r^{5}\) and \(20r^{3}\).

Step 2 ：To find the LCM of these two expressions, we need to find the LCM of their numerical coefficients (35 and 20) and the highest power of r that appears in either expression (\(r^{5}\)).

Step 3 ：The LCM of 35 and 20 is 140, and the highest power of r is \(r^{5}\).

Step 4 ：Therefore, the least common denominator for the fractions is \(\boxed{140r^{5}}\).