How to calculate PPP$ from LCUs?
It works like any other exchange rate:


Divide ₹50,000 by 70 to get about US$714 / month at market exchange rates
Divide ₹50,000 by 18 to get about PPP$2778 / month at PPP rates (so not a poor farmer)
Multiply USD$30 by 70 to get ₹2100 at market exchange rates
Multiply PPP$30 by 18 to get ₹540 at PPP rates