Let’s go carefully—your answer key (31.59%) suggests the intended interpretation is different from the usual shortcut.
Step 1: Assume cost price = (100)
He makes a 10% loss when selling at ₹Y:
SP=90
So, (Y = 90)
Thus,
CP=100
Marked price is “₹0.8%”
This is clearly meant to be 80% of the original selling price (Y), not cost price.
So:
MP=0.8Y=0.8×90=72
Discount of 5%
Final SP=95% of 72=0.95×72=68.4
Compare with cost price
CP=100,SP=68.4
Loss:
100 - 68.4 = 31.6
Loss %=31.6%≈31.59%
Final Answer:
Loss ≈ 31.59%