Shortcut Trick
Total Weight Ratio = 3 + 5 + 7 = 15 units
Original Price ∝ 152 = 225 units
Price after breaking ∝ (32 + 52 + 72) = 9 + 25 + 49 = 83 units
Loss = 225 − 83 = 142 units → ₹42600
1 unit = 42600 ÷ 142 = 300
Original Price = 225 × 300 = ₹67500
∴ The correct answer is ₹67500.
Alternate Method
Given: Ratio of pieces = 3 : 5 : 7, Loss = ₹42600.
Formula: Price (P) = k × W2, where W is the weight.
⇒ Let the weights of pieces be 3x, 5x, and 7x.
⇒ Original weight (W) = 3x + 5x + 7x = 15x.
⇒ Original Price (P1) = k × (15x)2 = 225kx2.
⇒ Price of pieces (P2) = k × [(3x)2 + (5x)2 + (7x)2] = k × [9x2 + 25x2 + 49x2] = 83kx2.
⇒ Loss = P1 − P2 = 225kx2 − 83kx2 = 142kx2.
⇒ 142kx2 = 42600
⇒ kx2 = 42600 ÷ 142 = 300.
⇒ Original Price = 225 × kx2 = 225 × 300 = ₹67500.
∴ The correct answer is ₹67500.
Additional Information
Variation Principles
When a quantity y is directly proportional to the square of x, the relation is y = kx2. If a whole is divided into parts, (a+b+c)2 is always greater than (a2+b2+c2), which explains the loss in such breaking problems.
Ratio and Sum of Squares
The ratio of the original price to the broken price is (Sum of parts)2 : (Sum of squares of parts). For a ratio a:b:c, the ratio is (a+b+c)2 : (a2+b2+c2).
Loss Calculation
Loss Percentage = [(Original Price − Broken Price) ÷ Original Price] × 100.