As we know Aryabhatta introduced 0 in calculation in 628BC, before that it was called as shoonya. So, my question is how was it interpreted in calculation during Ramayana time. Did they even know numbers or all addressed as thithis?
How they were even allocating the number of people for work during Ramayana time?
Firstly, zero was not introduced by Aryabhatta. It was discovered by westerners much later, probably through the works of Aryabhatta. In fact, the Hindu system of calculation has such exponents of 10 which do not have a name in modern calculations.
Zero did definitely exist at the time of the Ramayana, and so also the powers of 10, the calculation of which has been explicitly stated in the text.
Here goes Shuka describing the size of Bhagavan’s army to Ravana. One can see very high exponents of 10:
O King, a hundred thousand multiplied by a hundred, is called a koti and a hundred thousand such kotis make one shanku. A hundred thousand shankus make one maha-shanku, a hundred thousand maha-shankus make one vrinda. A hundred thousand vrindas make a maha-vrinda and a hundred thousand maha-vrindas make a padma. A hundred thousand padmas make a maha-padma and a hundred thousand maha-padmas make a kharva. A hundred thousand kharvas make a samudra and a hundred thousand samudras make an ogna. A hundred thousand ognas make a maha-ogna. That Lord of the Monkeys as also Bibishana with his counsellors are surrounded by a hundred thousand shankus, plus a hundred thousand maha-vrindas, a hundred padmas, a hundred thousand maha-padmas, a hundred kharvas, a samudra and a maha-ogna. a koti of maha-ognas and a thousand samudras, and that Sugriva has come to make war on you.
-Śrimad Vālmīki Ramayana, Yuddha Kanda, Chapter 28, verses 33-41
The above example helps one to see how monkeys (workers) were allocated to each unit. How many which monkey general has under him.
Another example showing the multiples of 10, from the encounter between Hanumanji and Surasa:
Having said this in anger, Surasa extended her jaws to the width of forty miles and Hanuman increased his girth accordingly; thereat Surasa enlarged her mouth to fifty miles, and seeing the jaws of Surasa wide open with its long tongue, terrible to look upon, resembling a mountain, measuring fifty miles, Hanuman enlarged himself to that extent also. Then Surasa increased her mouth to sixty miles and the heroic Hanuman to seventy, whereupon Surasa widened her jaws to eighty miles, and Hanuman, resembling Fire itself, to ninety miles. Then Surasa enlarged her mouth to the extent of an hundred miles and Hanuman, reducing his body like a cloud to the size of a thumb’s breadth entered into her mouth.
-Śrimad Valmīki Ramayana, Sundara Kanda, Chapter 1, verses 162-167
So yes the knowledge of zero was very much there during the time of the Ramayana.
Aryabhata was an expositor of the mathematics involved primarily in Jytotisha calculations. As such, he was actually not an inventor of either the place-value system, or the brahmi-arabic symbol for zero (Ifrah,Bibhutibhushan book, B Datta, A Singh-Chapter I, parts 8 and 14, and also wiki); contrary to popular opinion. The place value system was there in the vedic conception since antiquity. He just gave a compendium of the mathematics already available in a concise form relevant to those times and circumstances.
And, moreover, Aryabhata was there during the period of 476-550 AD, not sometime in BC.
