The ancient Indians had ‘Rule of Three’ , known today by the name proportion.
The ancient Indian astronomers had ‘continued Fractions’. They had no infinitesimal calculus, as it is said today. But they were taking limits, doing differentiations, integrations, computing involutes, evolutes, envelopes of curves for their requirement in astrological computations.
In ancient and medieval world, knowledge propagated from India through trade routes through land and through sea. The decimal system, the 0, the ∞ , the rule of three, trigonometry, spherical trigonometry especially, astronomy, medicine, surgery literature, etc. were India’s contributions to the world. India was most prosperous and most sought after juggernaut of a nation in past millenniums.
This monograph is my humble attempt to equate Rule of Three to Continued fractions and Continued fractions to differential calculus, and integral calculus at the elementary level. The tools the ancient Indian Astronomers had.