Q.A wholesaler offers successive discounts of 20% and then 10% on a list price of ₹10,000. Find the net price and the equivalent single discount rate.

Apply each discount in turn to the price remaining after the previous one, then compare the net price with the list price to find the equivalent single rate.

After $20\%$: $10{,}000\times0.8=8{,}000$. After a further $10\%$: $8{,}000\times0.9=7{,}200$.

Equivalent single discount $=\left(1-\dfrac{7{,}200}{10{,}000}\right)\times100=28\%$.

Here $L=₹10{,}000$, with successive discounts $d_1=20\%$ and $d_2=10\%$.

Step 1 — Apply the first discount.

Step 2 — Apply the second discount to this reduced price, NOT to the original ₹10,000.

So the net price is $N=₹7{,}200$.

Step 3 — Find the equivalent single discount rate.

Note that this is less than the naive sum $20\%+10\%=30\%$, because the second $10\%$ discount was computed on $8{,}000$, not on the full $10{,}000$.

Adding the two discount rates directly ($20\%+10\%=30\%$) and computing $10{,}000\times0.70=7{,}000$ as the net price is the single most common error with successive discounts — the true net price, $₹7{,}200$, is always higher (i.e. the true discount is always smaller) than this naive addition suggests, because each discount after the first is applied to a smaller base.