Let the selling prices of the three dresses be in the ratio 5 : 6 : 7.
So, let:
D1 SP = ₹5x
D2 SP = ₹6x
D3 SP = ₹7x
Step 1: Find Cost Prices
D1: 20% profit
CP1=1.205x=625x
D2: 10% loss
CP2=0.906x=320x
D3: 30% profit
CP3=1.307x=1370x
Step 2: Total SP
SP=5x+6x+7x=18x
Step 3: Total CP
CP=625x+320x+1370x
Using a common denominator of 78:
CP=78325x+520x+420x
=781265x
≈16.218x
Step 4: Profit
Profit=18x−16.218x
= 1.782x
Step 5: Profit Percentage
Profit %
=16.2181.782×100
≈10.99%