A wholesaler offers a bulk order deal where a 10% discount is applied to orders above Rs. 15,000, and a 5% additional seasonal discount is available. What is the effective price paid for an order worth Rs. 20,000?

Correct — A. Rs. 20,000 is above Rs. 15,000, so the 10% applies. The key treats the 5% as successive, taken on the already reduced price.

After 10% off: 20,000 × 0.90 = Rs. 18,000
After 5% more: 18,000 × 0.95 = Rs. 17,100 → option (a)

Single equivalent: 10 + 5 − (10 × 5) ÷ 100 = 14.5% off, and 85.5% of 20,000 = 17,100.

Why the others are wrong

• (b)
  Rs. 17,500 — Rs. 17,500 is 12.5% off Rs. 20,000. Neither reading of the two discounts gives that: successive is 14.5%, added is 15%.
• (c)
  Rs. 17,000 — Rs. 17,000 adds the discounts into a flat 15% of Rs. 20,000. That takes the 5% on the full price, not on the Rs. 18,000 left after the first cut.
• (d)
  Rs. 16,800 — Rs. 16,800 is 16% off, more than even the two discounts added together (15%). No reading of the stem reaches it.

Successive discounts multiply. They do not add: each one is taken on the price the previous one left.

Two discounts of a% and b% equal a single discount of a + b − ab⁄100 %. The ab⁄100 term is the part of the second discount that would have fallen on money already taken off: here 5% of the Rs. 2,000 cut, which is Rs. 100.

Key facts

• Successive discounts of a% and b% = a single discount of a + b − ab⁄100 %.
• 10% then 5% is a 14.5% discount, so the buyer pays 85.5% of the price.
• Successive discounts give the same final price in either order.

Common traps

• Adding 10% and 5% into a flat 15%: that lands on Rs. 17,000 and ignores that the second cut works on Rs. 18,000.
• Taking the 10% on the Rs. 5,000 above the threshold alone: the discount is on the whole order, and that reading reaches no option.

No directly related past PYQ was found.