A sold a watch to B at a gain of 20% and B sold it to C at loss of 10%. If C bought the watch for TK. 432 at what price did A purchase it?

Question: A sold a watch to B at a gain of 20% and B sold it to C at loss of 10%. If C bought the watch for TK. 432 at what price did A purchase it?

Solution:
A purchase at x taka
Selling price of A = purchasing price of B = x + 20% of x = 1.2x

Buying price of C = 1.2x - 10% of 1.2x = 1.2x - 0.12x = 1.08x

1.08x = 432
⇒ x = 432/1.08 = Tk. 400