Add GST: Total = Amount × (1 + R/100); Remove GST: Base = Amount ÷ (1 + R/100)
Add 18% GST to ₹1,000: 1,000 × 1.18 = ₹1,180.
'Add' calculates the final price from a base price; 'Remove' extracts the base price from a GST-inclusive total.
Yes, the formula applies to any percentage-based tax added to or extracted from a price.