Ganita Sara Sangraha is the name of the treatise written by Virasena.

Virasena lived in the 9th century.

Ganita Sara Sangraha primarily covers the topic of arithmetic.

Ganita Sara Sangraha is significant because it provided a comprehensive overview of existing mathematical knowledge at the time.

Trigonometry is not covered in Ganita Sara Sangraha.

According to Virasena, the rule for finding the square root of a number is $$\sqrt{a} = \frac{a}{4}$$

According to Virasena, the rule for finding the cube root of a number is $$\sqrt[3]{a} = \frac{a}{27}$$

According to Virasena, the formula for finding the sum of the first n natural numbers is $$S_n = \frac{n(n+1)}{2}$$

According to Virasena, the formula for finding the product of the first n natural numbers is $$P_n = n!$$

According to Virasena, the formula for finding the nth triangular number is $$T_n = \frac{n(n+1)}{2}$$

According to Virasena, the formula for finding the nth square number is $$S_n = n^2$$

According to Virasena, the formula for finding the nth cube number is $$C_n = n^3$$

According to Virasena, the formula for finding the nth pentagonal number is $$P_n = \frac{3n^2-n}{2}$$

According to Virasena, the formula for finding the nth hexagonal number is $$H_n = 2n^2-n$$