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A sells a bicycle to B at a profit of 20% and B sells it to C at a profit of 25%. If C pays ₹1,500, then what did A pay for it?
₹1,125
₹1,000
₹1,100
₹825
₹1,000
Work backward from C's price using successive percentage multipliers: A=1500×125100×120100.
A sells a bicycle to B at 20% profit, B sells to C at 25% profit, and C pays ₹1,500.
C=A×(1+100P1)×(1+100P2)
Work backward from C's price using successive percentage multipliers: A=1500×125100×120100.
Do not subtract the profit percentages from 100% or add them directly (20% + 25% = 45% is incorrect because profit is applied successively).
Define variables and relationships
Let A's cost price be x. A sells it to B at a 20% profit, so the selling price to B (which is B's cost price) is 1.20x.
SPB=x×100120=1.20x
Calculate B's selling price to C
B sells the bicycle to C at a 25% profit on B's cost price. Thus, C's purchase price is 1.25 times B's cost price.
C=1.20x×100125=1.20x×1.25=1.50x
Equate and solve for A's cost price
Given that C pays ₹1,500, we equate 1.50x to 1500 and solve for x.
1.50x=1500⟹x=1.501500=1000
B is correct because working backward from C's price of ₹1,500 gives A's cost price as 125×1201500×100×100=₹1,000.
This successive percentage change formula is identical to compound interest and successive discounts used in commercial arithmetic.