
Shortcut Trick
Effective discount of successive 30% and 30% = 30 + 30 − (30 × 30) / 100 = 51%.
Difference in effective discounts = 51% − 50% = 1%.
The difference in the bill amount is directly equal to the 1% difference in discount.
1% of Cost = ₹43 ⇒ 100% of Cost = ₹43 × 100 = ₹4,300.
∴ The correct answer is ₹4,300.

Alternate Method
Given:
First shop offers a flat discount = 50%
Second shop offers successive discounts = 30% and 30%
Difference in the final bill amount = ₹43
Formula Used:
Effective discount for two successive discounts a% and b% = (a + b − ab / 100)%
Cost = 100%
Flat 50% Off
Bill 1 = 50%
30% and 30% Off
Bill 2 = 49%
Diff = 1%
1% = ₹43 → 100% = ₹4300
Calculations:
⇒ Let the cost (marked price) of the shirt be ₹x.
⇒ Bill amount from the first shop (after 50% off) = x − 0.50x = 0.50x
⇒ Effective discount by the second shop = 30 + 30 − (30 × 30) / 100 = 60 − 9 = 51%
⇒ Bill amount from the second shop = x − 0.51x = 0.49x
⇒ Difference in the bills = 0.50x − 0.49x = 0.01x
⇒ We are given that the difference is ₹43.
⇒ 0.01x = 43
⇒ x = 43 / 0.01 = 4300
∴ The correct answer is ₹4,300.

Additional Information
Successive Discount Formula
When two discounts of a% and b% are given successively, the equivalent single discount is derived directly using the formula (a + b − ab/100)%.
Marked Price and Selling Price
Selling Price (Bill Amount) = Marked Price − Discount. The absolute difference between the two bill amounts equates strictly to the difference in the applied discount percentages calculated on the Marked Price.
Three Successive Discounts
For three successive discounts a%, b% and c%, apply the formula first to find the equivalent of a% and b%, say d%. Then apply the formula again for d% and c% to find the final effective percentage.